My first 'device' was a belt/cup/thong made of sheet metal/flashing, duct tape for holding the shape of the 'cup', then some 3/8"-thick foam to cover any areas that made contact with the skin. I used a standard small hasp and padlock on one side to 'secure' it. Didn't take too long to construct and it felt right? With just enough padding inside the 'cup', I was able to drastically restrict any erection.. I later added a PVC tube cut to fit inside the cup that forced my penis in a certain position like I imagined a 'real' belt would have. It worked really well but wasn't exactly wearable beyond a self-bondage 'scene'. I think I spent a total of $20-25 on materials. The PVC portion can be found at just about any hardware store. It's used as part of a sink 'trap' series of pipe pieces and other than trimming the excess length off, some sanding down the rough edges inside was all that was necessary.
There are plenty of the parts on this page that can be used for a 'tube'!
https://www.lowes.com/pl/Under-sink...air-Plumbing-parts-repair-Plumbing/4294822043
That was 'fun' and was part of a position and mobility restricting set-up.
To be honest. The money I have spent on other devices as mentioned from China have mostly been winners in my book. That original belt is now shredded in a landfill someplace and I'm okay with that! I have a custom cage that is my daily wear device, but have also invested in a fairly cheap 'belt' that I've worn once and seems to be a great copy of something that might be found at Fancysteel.com.au without the hefty price tag. Then there are all the other chinese gadgets that one must try then determine if they meet your needs, need to be tossed, or can be modified to meet your needs.
Best I can offer on this topic. Wish you and anyone else the best with finding your way!