I just picked up a like new pumped OS 91 four stroke for $100 minus the muffler.

Then engine was used once, crashed and repaired to like new condition. I borrowed a muffler from a new non pumped 91FS I purchased recently and tested the engine and it runs great.

Only problem is I just looked up the price of a new muffler and it's like $65 from Tower. Anyone have an idea where I might get a less expensive alternative?