Going with the proton pack from the game opens up some flexibility for me -- instead of being a "retro recreation" suit, this will be a more contemporary thing. Surely as ghostbusting has evolved over the past thirty years, the equipment will have done so as well. So I'm not real worried about making an exact reproduction of the belt gizmo, so much as something that works as a modern analogue. I used to have a bunch of old, dead video cards -- I might use one of those as the base.
The last piece that will then need to fall into place are the goggles; I don't plan to have a PKE meter or trap as part of the ensemble (although I might add a PKE meter later if the opportunity presents itself). Like the proton pack, I'll probably get goggles from eBay, as my own crafty chops are probably not up to the task. The belt gizmo, I can probably do myself.