My local has Weaner Rats that are just marginally larger than an Adult Mouse. I feel if the snake can take an Adult Mouse then the WR would be fine. For a Hopper Mouse equivalent, not 100% sure off the top of my head but if your pet shop/breeder/supplier has a large range you might just need to visibly compare them.
I breed my own now, so I don't really follow the preset weights/sizing too much anymore. Local pet shop is about $17-$18 for a single Jumbo Rat (250g+), not paying that anymore.