Mitrowski welding supply in Houston, Tx. Check with them ovation ally they have some good reasonable refurbished units. If its new you want, they have always had what we need. Also check out Alfab corp. I'm not sure what you're doing but I have bought positioners and rollers from both with no problems. Hope this helps.

Might also try Red-D-Arc.  I know they sell old machines might have positioned as well.

If you did not find a positioner you may want to try Weld Plus positioners in Cincinnati. They have new, used and rebuilt positioners in stock.
It will save you freight as compared to buying out of Texas.