I have an old but new G20 motor, .23 displacement, control line motor. I need a muffler. Do you know of one that would fit this little motor?

We're sorry, but the old SuperTigre G 20/23 has been out of production for nearly three decades. We'd have nothing for it at all. Your best bet is to check with those people who sell parts to engine collectors, or to ask in the swap shop areas here on RCU.