I've read that an Suzuki LT250r is the next size bigger, 12mm I think while ours is 10mm.
you'd need the correct mm drill and 12mm tap in correct thread pitch to do it.
advance auto also sales self tapping drain bolts for use in aluminum oil pans, I have one in my Jetta's aluminum pan, no leaks yet 2+ years later.
I think these labeled "oversize" are the ones....
http://shop.advanceautoparts.com/we...ersize&vehicleIdSearch=-1&searchedFrom=header
whatever you do, the plug cannot extend in further than the original or it will hit the shift drum and you may only have 3 gears < it happened to old member speeddemon before