I experimented some years ago with Continental belts (rather than the Gates ones Ducati use) for my SS.
I took my old Gates/Ducati belts to an engineering shop to buy genuine Gates belts. (It annoyed me that the Gates belts were made in UK for peanuts, exported to Bologna and put in carboard box then imported back to the UK at many times the price).
Anyway, the shop didn't have Gates belts but did have identical Conti belts for about £5 each.
They worked a treat but everyone I spoke to in this forum thought I was nuts.
No reason you shouldn't buy Gates belts from a Gates retailer. I notice that the latest "Ducati" ones from Bologna now have the Gates logo etc on them, rather than being printed "Ducati".