So-called "octave fuzzes" create an extremely distorted fuzzed octave up sound, but they are not surgically making a clean upper octave and only fuzzing it--they are distorting the whole signal to create their effect.
Multi-band distortion/fuzz pedals from Iron Ether, FEA, and a couple other brands are designed to have completely separate amounts of distortion on the lows, mids, and highs.
You could run a clean octave-up effect (EHX POG for example) into its own fuzz, and then use a blender (Boss LS-2 for ex) to mix that with your clean signal.