Given how the suit itself is custom, and the rest of the straps on the 2016 Proton Packs are generally considered custom (but inspired by some similar-looking real-world items), my money’s on the waist strap also being custom-made for the production.
Alot of folks have used alice frames and covered the straps with orange material. The straps are padded piece that attaches to the motherboard. A few folks on here have found a very similar set of straps on a hiking backpack. Unfortunately the back pack is pricey especially if you plan to cut it in half. However Molle frame straps have the exact configuration of the reboot straps, hip pad and all. the only issue is that you’d have to cover them with orange since they only come in digital camo and black.