At the very least, what you can try doing is sending these sellers an e-mail asking them where you might be able to find parts for your particular rig. You might also consider sending a PM to RushRC (forum sponsor) and asking him if he has any connections to parts.
As for turnbuckles, one thought is to see if another model's turnbuckels will work. Maybe take it to your LHS and see if you can try fitting some on there, then replace the set. Just a thought.