Probably the reason nobody replied is that there are quite a few options available to replace that flat drive belt. You can go with commercially available products which include leather or composition materials either glued or "Clipper" laced. All you have to do is supply the desired length of belt.
Or you can produce a "do it yourself" version, again using leather belting, composition belting, or the popular use of an automotive serpentine accessory drive belt. And here again there are options of gluing up a belt, lacing a belt using the method shown in South Bend's How to Run a Lathe book, or you can get yourself a "Clipper" lacing vise and install the laces yourself.
You'll find a wide range of options as to the best method. I can tell you that in my own experience I have tried almost every variation of the options. So far the best has been a commercial composition belt supplied with the proper glue which I glued myself. I did that more than 40 years ago and the belt is still running. But I have also had really good success recently on my 10L machine using an automotive serpentine belt and fastening it with a small "Clipper" lacing vise I bought on eBay along with a couple of strips of stainless steel laces, also from eBay.
The choice is yours!
