I tried setting up a bike shop after i retired but in this part of the US there is little interest. To cold to ride for 6months of the year and most of the bikes now are so cheaply made and disposable that its just not worth it for people to pay to have them repaired. You can go to commie mart and buy a bike cheaper than you can replace the innertubes for. Very sad thing they, big business, have taught our young folk that the only way to live is to buy brand new and then throw it away instead of keeping it repaired. Why i love my MGB i can still buy every part for it and fix it myself.
Back on topic Why not just make a template out of leather shaped just like a belt with the holes and end cut to shape, lay it down on your belt blank and mark the holes trim the end and your done.