So mine was made by a guy that got killed for fucking someone else's wife at a gunshow...
He did a GREAT job though!
Soft, flexible cow hide... But two layers double stitched makes it so it's soft and "loose" like a regular belt but simply WILL NOT fold over. Thick enough to fit the holster belt loops exactly, not so thick they don't fit the pant loops. Custom is surely the way to go if it's a possibility.
Now if I had to order one from someone, I'd for sure get the Milt Sparks belt, they take that shit seriously and their VM2 holsters are just the end all be all for IWB carry IMO. Well made, well thought out. Will probably last a lifetime like the one I have.
For interim or for a backup, I like the Galco belt. Nothing special, it's relatively cheap, thin and looks more like a cheap walmart belt than does the custom or Milt Sparks belt. It's two thin layers of leather (or something that looks like leather?) with a piece of stiff plastic inbetween. It gets it done and way better than just a belt.