RE: Evolution .46 muffler screw needed
OOPS!
So, that is not the 'muffler attachment bolts', but the long screw that holds the whole thing together...
I answered automatically... You can probably get a small diameter threaded rod, with appropriate lock-nuts and washers, at the same hardware supply...
Tower does not seem to list spare parts/components for this muffler, so you're pretty much on your own.