Thought I'd started a thread a while back but can't find it.
Masterfett suggested TriGate Creations in another thread as a possible source for some Custom parts but they don't appear to still be active and neither do Slayer Design Studios).
Anyone interested in creating an up to date list of who is still in the business of selling Custom parts?
If so, feel free to add them here (and if you can provide links so much the better).
Mods, feel free to move this to somewhere more appropriate if necessary.