Looking for information/recommendations for chair seat upholsterer.

Nominally just foam covered fabric on plywood base. 

Chair making group ought to have some good input on this.

Jules Siegel

Jules, why not do it yourself? Slip seats are easy! That is unless there is sewing involved in your design. A pneumatic stapler makes it easy, but you can use a manual staple gun if you don't have the pneumatic one.