That small clump may be too big for a punch excision, and I'm not sure "cutting and removing tissue" is necessarily the best route either.
Quite frankly, I would have thought the "breaking up" of matter via cannula should have been sufficient enough to improve it a good bit, enough where only you can detect it, or at best, resolved altogether.
You can look into
Androfill if you don't mind the flight - they may offer to provide
Revision since they do
Ellanse injections, which creates
Girth much the same way
PMMA does. I don't know if (a) they'll take on work performed by other Clinics or (b) the costs, but it's worth a shot. If money isn't an issue at all, you can always inquire with
Avanti Derma, who has dealt with
PMMA Revision moreso than any other Clinic I know of.
Good luck.