She might not want them as much as she thinks after she tries them, but check a kid-oriented bike shop, somebody that sells BMXs, or look around for a low-rider place (low rider bikes are big here and we have a couple of shops). Any bike dealer probably can order them for you from someplace like QBP, or you might find an bike you can cannibalize at a thrift shop. I've scored some really good deals at the Salvation Army.
When she tilts up and back, you may have to adjust the tilt of the saddle or even buy a new one. That changes the weight distribution on the bike, puts more weight on her butt and can be uncomfortable.