I couldn't find one either it looks like a molder one piece belt that they tube mold and cut to width. I will run a long board through it and feel for the dip.
Now I got to get a new vacuum, the sander is stinking quiet, I can run it and still talk to people in the garage, until I turn my vacuum on.
I've found 1 handle rotation = about .015 is that you guys come up with. And did you glue some sand paper to your sleds to stop slippage.
Thanks
Cory