If there's wider interest in a solution I can put together a couple options for you guys. We supply stub axles and hubs, in addition to the transmission components, to several professional racing teams.
One option could simply be a recreation of the existing stub axle with different splines to accept the X tracker. I haven't setup an account with SKF yet, but have a contact there and don't think it would be an issue to supply the bearing, as well as the axle.
The other option could be a redesign around a race bearing and a hub designed for it.
Howard - if you'll shoot me the drawings of the stub axles and a few photos of the axles/hubs I can get a rough idea of pricing and we can go from there if interest exists.
Best,
John