I picked up an old Schwinn as part of a 5 bike lot (it was a good price) that is missing both it's seat post clamps and the seat The seatpost is 13/16" and the top portion is 5/8". Since I'm flipping it, I'd like to fix it up for as little as possible (it's only a Caliante); I've looked online and I've seen the Wald seat posts, but to avoid the bending issues, could I just use a pipe or shim to take the clamp area from 5/8 to 7/8? and what options, other than overpriced used/NOs on ebay are there for the seat post clamp (not sure of terminology - the one that stops the seat from going up and down and spinning)?
any help would be appreciated- Thanks!

You could just use a 5/8" clamp or am I missing something? If you are having a problem finding one cheap email me offline. I probably have a couple hanging around.

Thanks - Actually just got some from someone local today