Sorry for the bad news, but getting rooted cuttings of this plant would be illegal! It's covered by Plant Patent #15,925 and cannot be legally propagated or sold without a license from the patent holder.

You can legally purchase the plant from a number of sources on the internet. As always, check Garden Watchdog for ratings before buying from any nursery you aren't familiar with. All reputable medium to large nurseries (and almost all small ones) will be rated there.

Here is a link that might be useful: One of many sources - Klehm's Song Sparrow Nursery