Regarding track links etc:
Try the Czech Republic. They have some impressive manufacturing capability and long experience with that sort of product. Closer than China, for starters.
Anyone thinking of a DIY 38T or Hetzer might take a look there, as well.
If you have a few parts left over from this current project and can find (or fabricate) a 10.5cm Le F.H 18/2, you could run up a Sd.Kfz. 124 "Wespe".
Cheers,
Bruce