They stopped making the BB dynamos a while back. Sanyo was the most well known. Soubitez made one too. There's a few hokey bolt on modern generator gizmos available if you look for them. Or you could try to buy a vintage one. They weren't that great anyway. Tended to break after a while.

If you don't want to spend a lot of money, or even if you do, IMO the best choice is a modern LED battery light. I love my cygolite. They unclip usually. Have your friend take it with her when the bike is locked.