I think you want an old-fashioned fork-mounted light - ges on behind the brake. I like them because they are not easily removable, so you don't have to take them off when parked. Nirve makes one (http://www.amazon.com/Nirve-Vintage-...8989037&sr=8-3) although it's probably more of a "be seen" than see. I know there are better ones too. I had one I got off ebay that fell apart.
http://lovelybike.blogspot.com/2009/...igh-ladys.html Velouria mounted a suntour version thatlooks nice, but I don't know where to find one.