Where can I buy leopard tadpoles in the Chicago area?

I want to have the girl I nanny watch them change into frogs, and all I can find are bullfrog tadpoles, which can take up to 2 years to change. A 4 year old does not have that patience! I've considered ordering them online, but I feel like it's much more expensive (especially since I already have a tank). Does anyone local know of pet stores that specifically sell leopard tadpoles?