You can get a busch and muller bottle generator at a pretty reasonable price direct from a German mail order company like this,

Busch & Müller Dymotec 6 light travel dynamo

I haven't used one but I've been thinking of getting one as well. I used bottle generators in the past and they weren't bad. This, at least according to the reviews I read, is pretty decent quality as are B&M products in general.