I got Jake this Spring. It came with a straight pipe and remnants of a muffler. Very loud. After trying to find a muffler to fit it with no luck, I decided to make one. I started with a muffler off a B&S 15HP OHV engine. This had something rattling around inside, so I took it apart to investigate. Found the guts had fallen into several pieces. After a little trimming here and there, I came up with a new piece for the inside. I opened the holes up to match closer to the Kohler K301 exhaust. Found a piece of auto exhaust for a new inlet pipe. It sits further out than a stock muffler, but it has a longer body and this also gives me good access to the dipstick.
Here's a pic from when I got it.