I don't know if you've already found a tool that works for you. But, there's:
ShaderMaker
http://cgvr.cs.uni-bremen.de/teaching/shader_maker/
which is cross-platform (I've tested it under Windows and OSX)
and
glman
http://web.engr.oregonstate.edu/~mjb/glman/
which is windows-only but, according to the authors, will be ported to mac eventually.
