Look for a muffler on Ebay or any of the other auction sites. If it's an engine from the 60-70s, it may not have been provided with a muffler. Many older R/C engines had a baffle linked to the carb. which opened and closed along with the carb., so a muffler would not have been designed for it. This makes muffling these engines difficult, as there is little after market equipment available now. Back in the 70s there were muffler manufacturers providing mufflers for these engines. Semco, Tatone and others come to mind. These folks made aftermarket mufflers for most engines available at that time. However, each came with an adaptor for a specific engine. I have an Enya .19 and an O.S. .60 MAX H with the same problem. Good luck, with your search!