I would look into moped exhausts (tho the manifold will need a bit of tweaking to get it to fit) there's also "poo-poo" pipes, much like the stock one but with a much longer head pipe so the muffler itself is more toward the back of the bike, behind you instead of under
I dunno where to get a poo-poo, I'd check Spooky, I think
they might have them, but a moped exhaust might look better and be quieter - if a little more work.
If you dig around the forum some - there's actually quite a bit on quieting these MBs, the intake is responsible for a LOT of the noise you hear. I found when I made a silencer for mine that it had been actually louder than my exhaust was.
Good luck man, I too like the "stealth" approach