There's only been 3 waves so far and the last one feels like it might be the last, as it wasn't anywhere near the quality of the first two (usually a bad sign for a line.) A random mix of Heisei belts, only going up to Hibiki, or rather, Zanki, and for some reason they're all hard-plastic, and not actual flexible belts like in the first two waves (which you could wear like a wristwatch if your arms are thin enough.) Also, they're pretty big, if you want something that would fit Figma or Revoltech, they're a lot bigger.
The SH Rider 1 & 2 from Kamen Rider THE FIRST had removable belts as I recall, though the buckle was a separate piece so you'd have to muck with it (I might be totally misremembering here though.) I've seen some people do stuff with those before.
Most of the HD figures are almost the right size, but you'd have to cut them up probably. In general there aren't a lot of good removable belts in that scale that I've seen.
I dunno, but I am looking for pretty much the same thing for a custom figure, so if I find any more I'll let you know!
