I don't think that sky tracks exists anymore (as sky trac) and I'd try to find out who bought them and do they still support it (parts).
JLG has absorbed quite a few of them. The good thing about this machine is it's probably very basic due to it's age, and "mechanical" vs. a bunch of electronics and proprietary electronic components and keeping it operational especially for occasional use shouldn't be too bad.
I'm not an expert but the any boom anti friction or roller parts would be my concern. Everything else should be simple hydraulics with the possible exception of the transmission and axles (brakes esp.), but both of these are probably "by others" and used in/by many other manufacturers and someone supports them. Finding them might be the challenge.