Since I don't have a physical walk-in store most distributors will not deal with me. A few will; click the "Vendors" link on the start page to see some of them. A lot of manufacturers aren't interested in supporting rare, obsolete series - especially in small lot quantities. There are a number of mfg that don't deal directly with merchants; distributors only. There are also mfg and/or distributors that don't like to have their products sold at too many places. They tend to feel that certain areas are sufficiently "saturated."
Exhausts are no longer made. Every year; every model is a bit different. There are some still sitting in warehouses that get sold off in batches at pennies on the dollar. I pass these up as I lack space to store them and every year is different; and more importantly: most of these exhausts are quite loud and designed for boulevard cruisers. Not a good fit with our philosophy of what a sporting twin should be. A late entry: Niche Cycle lists a Gen I two-into one exhaust that is currently back-ordered. It could be adaped to any XV bike. However, thus far all of my customers who have gone full-tilt on modifiying the motor have opted to build (or have built) their own one-off equal-length header exhaust; not an inexpensive proposaition.
One that I can't help with is Motion Pro cables. I am in Orange County and Southern California is saturated with their merchants. Again, every year, every model is different. I leave it to the customer to send measurements and particulars to them. Expect about sevemtyy dollars per cable. Soon I will offer cables from Niche Cycle so this is really moot. Before I leave this topic: please do not run 1) a single carb manifold, 2) Bing, or 3) Dellorto carbs. These last two are using twenty plus year old technology.
Another brand I cannot provide is Barnett Clutches. This is because I don't have a physical store. Note also: I have never seen an XV built enough that a fresh stock clutch slipped under any (unintentional) circumstances. The only time a clutch has slipped for me is when I tried using Marvel Mystery Oil as a lubrication additive. So, I don't recommend running an after-market clutch. Or if you have a thousand or smaller bike, don't bother trying to adapt an eleven hundred clutch; it has the same number of steel and friction plates. The steel plates are simply thicker. You'd have to run the late model rightside engine cover, and why would you want to give up any ground clearance for a right turn? The exceptioin is if you want to build a dragaster or LSR bike; in these cases you would probably want to adapt a dry clutch with a larger swept area on the fricxtion plates. Maybe an automotive clutch?