Offset/ adjustable post for 2 3/8" base?

[Wee Hooker]

Just bought a new (mirrocraft) boat that has 3 pedestal bases for 2 3/8" straight tube posts. The boat came with 2 seats (with posts) but I'd like to set up a "butt seat in the bow to fit one of the bases. Having trouble finding a adjustable height ( 22-30" +/-) 2 3/8" post to fit the base. I'd particularly like to set up this one with an offset post but can only find offsets in narrowers sizes. Does anybody make an adapter to go on the more common narrower posts to get them to fit a 2 3/8" hole? Any input appreciated.