I know absolutely nothing about mice, rats is a different story though. I guess im not much help here, only thing I can suggest is breeding them, which is very easy. If you ever give breeding a though I would breed rats though, your snake never outgrows a rat so you can stick to only one rat a feeding. your snake is gonna outgrow mice very quickly and its gonna start taking a couple every feeding to satisfy them every feeding. Breeding them is the only option I can tell you unless you find another feeder source.