I thought of this thread as I was going through my mail the other day and dug it back up. January seems to be the clearance time for these machines, I think about getting one every year. This page features several styles by Champion from a unit you bolt to a post (sale price of $50) to one that takes what looks like a box of targets, self loads and oscillates (sale price of $1000). I agree with the above posts to buy the machine part you want and fab up the rest. You can build what ever stand and launch station you want, add wheels to make it portable, have a seat for a helper, storage rack for the targets, ammo, emptys, include a battery holder if you get the powered one, fab up a remote release cable, etc etc etc. Hey, I think I just talked myself into doing one myself this year, good family fun!
(edit: also have the standard ground mounts for $20 and do watch out for those shipping charges...)

This is from Natchez, but you can check out Midway or Cabelas, these are good companies to deal with.

http://catalogs.natchezss.com/F012010/full.asp?page=69