My advice is to get an accordion. They see you pulling it in and out, the sweat beading on your brow, the showy glissandos and mastery of the complex-looking bass buttons and all they can do is tip.
As an interesting aside, my 80-year old father was in town and listened to me perform with my XD3 arranger and Petosa reedless digital accordion and said it was nice. When I played Sorrento on my Excelsior accoustic he said it was incredible. He far preferred the accoustic.
Either way, patrons tend to tip accordionists rather well because it's so different. As a performing musician, I tip ALL musicians well, including the 16 year-old Vietnamese boy playing piano in a Los Angeles Thai Restaurant last week. His, uh, rendition, of Let It Be was one of the more interesting things I have EVER heard on a musical instrument, but hell, he was out there trying and deserved encouragement!
As an aside, did anybody catch the National Anthem at the Tennessee Titans pre-season football game last weekend? A defensive end for the Titans played the anthem on his Sax. Just looking for opinions if anybody saw it.