None of what I saw advertised rang my bell, so i decided to create my own, using sample illustrations as a springboard for my venture.
As it turned out, it was a snap to create. A couple pieces of real straight 1" x 2.5" x 24" poplar; a 1/4" piece of ply for the custom designed slip gauge; a hinge to attach the pieces of poplar; a turn-screw to lock the gauge down to a countersunk nut in the top of the anchor piece of poplar; a couple decorative craft dowels for handles; a small angle bracket bent to proper shape for an angle marker; and a small wedge-shaped stock stop glued to the leading edge to guide the material through the blade.
Voila! I gots meself a real taper jig to cut fretboards, and it cost me about $5 and a hour labor. What do you think? Perhaps this idea will work for you.
I'm getting set up here to cut a piece of exotic ziricote.
Once I've determined the angles I want, I'll mark the slip gauge, and any future cuts will be a snap.