Wait... I think I'm misunderstanding this one... you don't mean one small mouse everyday right?
I have a July bp and he is on adult ASFs now. I'm thinking that's equivalent to a small/medium rat. He eats one ASF a week.
Their heads are small but their jaws detach to open W I D E... so, you want to use a rat that is the same size around as the biggest part of the snake's body.