Have you considered a set of hardnes files?
http://www.flexbar.com/shop/pc/HARDN...-SET-p5383.htm
Not as precise, but a whole load cheaper and easier to store. That, and lets be honest, how many of us actually need to know the exact hardness of a blade? Ballpark is good enough for me at least, im perfectly happy with oxide colors and temperature control telling me the hardness