I did a little googling and found a breeders site and then starting looking for ones near me. I got 2.2 that way and I'm pretty sure I'm about to have a lot more.
The rat breeder did tell me to get an extra male so Big Papa would have a playmate. Might have just been a good upsell, but I did it anyway. I paid $20 ea for them I think.
Petco selling hopper mice for $5 has to be swimming in gold coins Scrooge McDuck style, I'm obviously in the wrong line of work.