If you find some of those skinny hose clamps, pick one long enough for the job, cut it in half, and attach it to either side of the muffler. Then use the worm drive to hold it to the engine. Just don't get real ham handed on the screw driver, or you will distort the case and pinch the cylinder. Another method is to use a strong spring to hold it on, or a bale type of retainer made from music wire. Some one did a real nice photo presentation of how to make home made mufflers using this method that was in the engine forums. Check that out. If you know some one with a TIG welder and they are up to the task, a lump of metal can be welded on to the case and a new ear formed. Also, some have JB-Welded an piece of tubing, brass or aluminum, to the side of the exhaust stack and case. This is best done when the engine still has both mounting ears. I have done all of the above successfully, with the exception of the wire bale, which I will try at the next opportunity.
Good luck with it,
Dan McEntee