Jumpsuit
So obviously the most important part of a Ghostbusters cosplay is the jumpsuit. You can probably go to the work uniforms section of someplace like Sear's and get one that works, but I made my own. I used this pattern from McCall's with a mid-weight khaki fabric.
For the orange reflective stripes, I ordered six of these iron on reflective tape packets, which came out to about ten feet. You need enough to have double stripes around your chest and both arms, so measure your bust and biceps and multiply the bust measurement times two, and the bicep measurement times four, then add those together. The tape comes in 32 inch packages.
I got this iron-on Ghostbusters logo patch for the sleeve. In the movie, all the Ghostbusters have name tag patches on their chests, which I didn't do. If you choose to do the name tags, there are lots of options on Amazon and Etsy.
Obviously, since all the Ghostbusters have matching jumpsuits, you can use this portion of the tutorial no matter which Ghostbuster you're cosplaying.
Wig
Holtzmann's got a pretty unique signature hairstyle. I'm not blonde, so I used a wig. I got the Tawny 1310 off Amphigory in #22. Style-wise this wig works, but it's a bit on the small side so it squeezed my head after a day at comicon and the adjustable sizing straps are velcro instead of hooks, so they get caught on the wig fibers, wig caps, and your own hair. Whether you're using a wig or your real hair, this Youtube tutorial is an excellent reference for doing Holtzmann's hairstyle.
Necklace
Another signature Holtzmann item is her Screw U necklace. I got a 3D printed pendant from Etsy and put it on a chain I already had. It's a little bigger than the pendant is in the movie and is obviously not metal, so if this option isn't the look you're going for, there are lots of other people on Etsy that make and sell Holtzmann's necklace.
Glasses
It can be really hard to find non-reflective yellow lensed glasses with side-visors without spending a lot of money. After some trial and error, I bought some cheap yellow tinted glasses off Amazon. I then used a paper towel tube, aluminum foil, and double sided tape to make the side-visors. Here's a tutorial I already made for how I did it. However, the visors fell off during and after comicon, so I'm going to be experimenting with better alternatives and will update when I've found a winner.
Shoes
I admittedly sort of forgot about doing anything specific with the shoes. I just wore combat boots, but you can wear rainboots like she does during the scene at the concert, or you can make boot covers for the ones all the team wears at the end of the movie.
Proton Pack
The hardest, most work intensive part of a Holtzmann (or any of the Ghostbusters) cosplay is definitely the proton pack. Mattel sells a toy version if you don't want to make it yourself and are willing to dish out some money. I made my own. Mine isn't perfectly screen accurate nor detailed because I didn't have the time and resources and I also wanted to make mine have a double function as a backpack.
The materials I used were mainly a bunch of random junk. I got a cheap plain backpack off Amazon and removed the front pocket and label. In order to stabilize it and make sure it won't collapse under the weight of all the hardware, I put a cardboard box inside. You should definitely do this first because I did it last and had to use industrial strength velcro to attach it, which barely worked, and if you do it first then you'll be able to use a stapler/staple gun/something else more successful because you won't have to work around all the stuff you've already attached to your backpack.
For the faraday cage, I used a banana basket I found at Goodwill. For the lights inside, I got a short strand of red LED rope lights from Ebay. It has an adhesive back, so I wrapped it around one of those plastic flower pot trays and stuck it on there. I then used a heavy duty needle and thread and tacked the lights and the basket onto the front of the backpack. I simply let the battery pack for the lights hang down into the backpack (remember to bring spare batteries to comicon in case yours wear out).
For the bottom of the pack, I cut a cardboard box in half so it fit the bottom of the backpack. I painted the sides silver and the front and bottom black, and painted diagonal yellow stripes across the top of the front. I then used industrial strength velcro to attach it to the backpack.
For the blaster, I got PVC pipe, cut two 13 inch sections, and painted them silver for the barrel and handle. I used an old alarm clock box and painted it silver for the center box. I measured out the circumference of the PVC pipe on the front end and used an Xacto knife to cut a hole, into which I inserted one of the pipes for the barrel. I duct taped it into place, then duct taped the handle pipe onto the side of the box, facing the other direction (you'll want reference pictures for this). I then hot glued some black craft foam around each pipe for handles. For the cord that connects the blaster to the pack, I got some random cords from the electronics section of the thrift store. I threaded one end into the handle pipe of the blaster and duct taped it into place, then wedged the other end into the center of a small thread spool that I'd painted silver. I duct taped the spool to the backpack to hold it in place. I made a holder for my blaster by sewing a 1 1/14" plastic plumbing coupling to the side of the backpack.
And there you have it! As a finishing touch, I added some fingerless leather gloves that I already had for Black Widow. By no means a requirement, but she does wear gloves in the movie. You can find lots more references, especially for the proton pack, in my Pinterest board. And now for the finished product:
Happy cosplaying!