Metal versions of these are available from here:
http://www.stewmac.com/shop/Tools/Special_tools_for_Neck,_fingerboard/Understring_Radius_Gauges.html

Find your fretboard radius, and set your bridge saddles to match. They're handy for matching pickup polepiece heights to the arc of the strings, too.

Each of these unique gauges has a radiused arc on both the top and bottom surfaces, and is shaped to fit easily under the strings.

The set of 9 gauges includes:
7-1/4", 9-1/2", 10", 12", 14", 15", 16", 17" and 20" radii.

They'll work for string spreads and fingerboards up to 2-5/8" (66.68mm) wide.

Use the bottom curvature to determine your fretboard radius, and the matching top curvature becomes a reference for setting string saddle heights for best playability.