Aspen shavings are in nearly all pet stores. If you cannot find any, wal mart stocks a bedding made from recycled paper, it's not real attractive, but it is dust free, and absorbent.
Rat feed? almost everyone carries a mix for hamsters and gerbils, I feed this to my breeder mice, and they beg for more.
Looking for a package that reads "rat food" is going to be a tough hunt!
Don't forget chew sticks, rats and mice will develop dental problems without something to keep the front teeth wore down.
A few drops of veggie oil on the exercise wheel axle will keep you sane. Unless you like to listen to the never ending squeal.
Good luck.
Wayne A. Harvey