I use Laynelabs, they don't have a minimum requirement, and have all mouse sizes from 1-day old up. The only downfall for me is that they ship from somewhere in California I believe, so shipping for me is around 40 bucks, but I back ordered enough for my only current snake, and the one I plan on getting sometime next year, to last a while. For my baby I got 50 1 day olds and 50 large pinks (enough to do easily for several months, 8+ I'd say) for only around 80 bucks. And I read (although this is my first snake) that when it gets full grown the cost of that will go down a bit. I live in the middle of no where, 150 miles+ from the nearest reptile expo, and I've looked everywhere online for mice breeders/fellow snake owners that are close and have found nothing
so I'm forced to buy online. BTW everyone who reads this, I'm in the WV, KY, OH tristate area..... If anyone is close lol