That really sucks man, sorry to hear that.
Maybe just try to buy a stock gy6 again, and Go with a thicker wall. My 58.5 mm is holding up. Plus you have a light single seater you don't need a massive BBK
Maybe you could use top end off these....
http://hudsonvalley.craigslist.org/mpo/4567355227.html
http://longisland.craigslist.org/snw/4520892066.html
http://jerseyshore.craigslist.org/mcy/4535400737.html