[14TLC]

For bike you can use C-TEK MXS25. It's very quality built and stable, though much cheaper alternative to everything else proposed here. Still provides up to 25A. In my early days I used two of these in parallel on E cars, and it worked flawlessly.

Thought about it. I also use other C-TEK products and I'm very satisfied with built quality. MXS25 ain't cheap either compared to other alternatives. Compared to dedicated automotive power supplies it has reasonable price. Locally is about 300 eur new.