A minor issue you might have wanted to address before getting a BP?
(I am in the same boat - which is why I don't have one.)
Your location says Chicago. If you are anywhere near there, there HAS to be something available somewhere. You might look up private rat/mouse breeders on Craig's list. Long term, you might also want to start you own breeding colony.
The BP breeder I corresponded with said that new born rabbits can work. There are lots of backyard bunny breeders. (I actually raise rabbits, but I can't guarantee a weekly supply suitably sized for a young snake - esp. during the summer months when they breed less reliably.)
Keep working on it.
Where there is a will, there is a way.
By the way, I am no expert, but that snake doesn't look skinny to me. (Maybe someone else can chime in if they see something of concern.) To my eye, she is vibrant and glowing. Breeding tells. She seems to be thriving, so you apparently have most of it right.