Just to chuck in my thoughts....I think a small pin badge is good idea but I think it should be a of such a nature that's it's recognisable by other ppruners but not by the man in the street. The wearer of a badge that actually said "Pprune" on it would probably spend forever explaining to people what it meant!
I second (or third or whatever) the idea of the little jumbo; how about
:
PS. I'll take several
