I found some trays at some restaurant supplies stores here, they are used for busing tables. The size is 20" x 15" x 6". I'm thinking of keeping 1.4 in them, but would they be big enough for 1.5?

I think the 6" height may be a bit too high for the mice. I'm thinking of putting some kind of "stool" at the side which they feed so they can reach the hardware cloth (I always find this name funny, we call them something like "wire net" around here..hehe)