Muffs. As in Oxford Handlebar ones. When I bought the Innova it had a set on. Made out of soft neoprene, I believe. Quite easy to swap around between bikes as well. Although they looked very strange on the Ninja...
There is a bloke round here who uses the 4 pint containers on his old school MZ, another has a Yam Divvy with a pair of semi skimmed guards. Both these guys regularly tour round Europe, so I guess they work.