What kind of after-market barrels can I get for my Maverick/Hornet?
Barrels for the Maverick are still made by Armson, J&J, and Taso.
As of this posting you can still buy a J&J Ceramic at http://www.paintballlover.com
or direct from J&J. You can get an Armson Stealth from Armson. I don't know of any places to get a Taso Eliminator but I'm sure if you look around you'll find one.