You can find Masur birch, which I think looks nicer than curly birch from
http://www.axminster.co.uk/default.asp,
http://www.craft-supplies.co.uk/ used to carry it, but don't seem to now, I include them because of all the other tasty handle materials that they carry.
When choosing a handle material, think about what you want it to do and what the properties of the wood are. Birch is fairly soft and light. Curly maple is a bit harder and heavier, and things like cocobolo, bocote, and rosewood are a lot harder and weigh a ton but are much, much, tougher.
Hope you find what you want,
Chris