GeorgeBoards™ has made some really nice and Low Cost nut and bridge sets with rollers for the palm benders.

This item is a Roller NUT only with Rollers spaced slightly wider than the original nut's spacings. 1/2" tall
This part fit to the width of the end of the fretboard.

A lot of folks are using these to upgrade their Gretsch 5700 lap steels as they add palm pedals.

This item will be the NUT only 

Important !! The zero point of the axel is 1/8" from the edge of the part you need to adjust where you place the part.