I had Central Wheel in the UK build a rear wheel on a Talon MX hub. With an Akront alloy rim, SS spokes, the hub and the labor it was maybe 400 pounds total. I am pretty sure three are multiple dirt bikes that have hubs that can be used on an XS, with some custom spacers for axle, disc and caliper. It is just a matter of taking some measurements, draw a sketch and start searching. For front hubs, l'm pretty sure RD350, RD400, SR500, XV535 are a direct fit. A lot of Yamaha bikes use the same disc bolt circle as the XS. And a lot of Ducati s as well.