Camera suitable for a 2 year old?

My two year old daughter has showed interest in photography and upon (carefully) letting her hold my Canon S90 she seemed to have a lot of fun shooting. So I'm considering getting her a camera, but which one?

Obviously it must be durable, easy to use without too many buttons etc., have decent battery life and take reasonably good shots. A real viewfinder (not just using the LCD display) would be a bonus in my opinion. And of course not too expensive. What's out there which fits the bill?