Good luck on trying to buy adult bullfrogs.
The few places that do sell decent size
bull frogs are expensive. I found one on-line
source but the adult size were $25 a piece!
And some of these for $25 are easily small enough
to be a $25 snack for a bass.

http://www.backwaterreptiles.com/frogs/bullfrog-for-sale.html

http://www.petsolutions.com/C/Live-Frogs/I/African-Bullfrogs-Pixie-Frogs.aspx

https://www.pondmegastore.com/shop/product.php?productid=16143

http://www.reptilesbymack.com/amphibians.aspx

Fishing has never been about the fish....