" I would have to find some square tube with the ID just bigger than the OD of what I've got."
They make 2-1/2" sq. tubing with a 1/4" wall. You might have to knock the sharp corners off the 2" tubing with a grinder though.
Drill a 1/2-5/8" hole through the whole works and "pin it" with a bolt & nut.
I'd think a 5-6" long "socket" would be adequate.