Hello!
Is there any conversion kit available for FFWD disc wheel for track use?

I do not believe there is. I have the track version, and one of the reasons that I picked it up is that it is track specific (as opposed to something like the ProLite). FFWD USA is a solid resource (even if they are not in charge of your territory ). In the end, I think you are better off looking for a trade with someone going the other way -- but make sure that it is Gen 2+ as they had some bearing tolerance inconsistencies with the very first generation.

There may not be an official track conversion kit, but would a set of bolt-on skewers work? I assume the problem is that tracks don't allow QRs because of the damage they can do to the wood, but bolt-ons are usually even cleaner than true bolt wheels.

Something like this:

that would work on the front but not on the rear

Yeah, for some reason I thought this was just about the front wheel. My bad.