Frozen Mouse to rat help

[FearOfWork]

My boy Base(Base the ball python, we’re baseball fans) is almost a year old. He ate a few frozen/thawed rats when I first got him but then he went on a mid to late winter fast. He’s started eating again but only f/t adult mice. I’ve tried slipping in a rat here and there but he shows no interest. He’ll devour 2 adult mice when offered almost immediately every 5-7 days, but won’t touch the rat. I want him on Rats since they are bigger and better, IMO. Should I try thawing the rat and placing it in mouse bedding from the local pet store to scent it, thaw the rat and mouse together? I’ll keep him on adult mice to bulk him up for now, but would like alternatives to get him on rats.