I've often seen a notation where there is a horizontal bar over a letter to indicate the inverted value of something, e.g. q and (not)q for the outputs of a flip-flop. The not q would be a q with a bar over it.
More recently I was trying to describe the inputs to a 16 bit ADC, where one of the lines was R/(not)C.
I just waded through page after page of Unicode but could not find Roman letters with bars over them, except a few vowels.
Is there a way to do that in a Stack Exchange post?