I've got a few around that size. I'm in the process of switching them over to rat pups from adult mice, which are the same size from my seller. I don't know the exact size in grams off hand, I think somewhere between 15 and 30? A few rat pups and weanlings/smalls (the next size up, some people call them differently) should be about what you need.

Pinks and fuzzy mice are way too small for a ball python of that size, as a freshly hatched baby can take a mouse hopper or a rat crawler.