Not a problem, Here are some links to get you started.
Here is a link to the blacklisted sellers on gbfans.
Use this one to help you avoid sellers that aren't reputable so you don't wind up losing money for something that never gets delivered to you after purchasing it, or getting poor quality parts. This list also covers sellers who sell recasted parts (meaning they bought the part from someone else, then created a mold from it to make a duplicate of the part to resell)
Now onto the sellers list, this by no means is a complete list, it's just something to help you get started.
First off here is the link to the GBfans store for the section for Proton Pack parts
I had previously mentioned Karnivorous Creations so here is a link to his website to look at the parts he sells. If you want to talk to Mike about having him build your pack for you, use the contact us link. Tell him Van from the North Georgia Ghostbusters sent you his way if you decide to go this route. http://www.karnivorouscreations.com/store
Another seller that makes great stuff is benofkent but he's in the UK so it may cost more to have stuff shipped to you. here is a link to his etsy store
You may also want to look into sourcing individual parts or kits from different sellers depending on how you want to build your pack.
ThrowingChicken here on GBfans makes a great Neutrona Wand / Particle Thrower kits
If he was still making and selling parts I would have also recommended Nickatron for parts, but he announced a couple of months back that he is no longer producing parts to sell.
Anyways I hope this helps to get you started. Good luck with building out your pack!
Be sure to either do a build post on GBfans to show the progress for your pack build, or to show off the completed pack when you get finished with it.