Tribal Owners Group was pretty active a couple of years ago, not sure about nowdays. Should have all the tech info you need archived though.
Tribal Owner's Group - Powered by vBulletin
Check their "What happened to Toxic Toys" subforum for some background.
A couple of the members there have websites selling some after-market stuff, I'll see if I can find a couple links.
[Edit]Found a couple but couldn't find any solenoids[/Edit]
Tribal-Paintball Products by Edwin H. Air Soldier Products
PBN's Tribal forum also had a lot of good information last I checked.