I think that's called a gimbal assembly but under "joystick" Newark sells these
http://www.newark.com/23M6940/passiv...DUCTS-M11Q061P
But they are a bit pricey and you'd probably have to change the pots to 100K if you want to use them for a FIRST OI interface.
Same with mouser
http://www.mouser.com/catalog/629/532.pdf
I think some RC transmitters have a gimbal assembly and if you know a type you might try finding one on e-bay for parts and salvaging the units.
Good luck
Steve