Take a look at
Surplus Center under their pneumatics section. They have all kinds of good stuff for things like this and if your lucky you might find just what you need at a price you like. Don't know what you are needing them for but you might also check out the
gas springs under Misc.
Oh yeah, another place you might find something useful and cheap is
Young's Surplus. I haven't bought anything from them in years but they were good to deal with when I did several years ago. If they happen to have something you want they have been known to haggle a little if you ask nicely.