I stock and sell the BDls they are the most poular and typically the first ones to have drives for the new models. Stay away from Primo they are out of business so whatever is available will be old stock and currently parts are available for the Primos but I dont see that being the norm for a long time. Tech Cycles is my next choice Billy at tech has always been good to me. They do crazy stuff back in the chopper days they built me a lot of cool drives. I stock pretty much all the parts for BDL's . BDL makes the PM drive as well.
I think this thread cursed me someone flippin cut part of my belt parked in the city so now I have to put a new belt on but unfortunately I am unable to find any info on replacing a BDL open primary belt. What I have found is people complaining about their CS and while I have no personal experience with it yet it does seem to be a popular opinion.