Well, I had a meeting tonight next door to home depot and I ran in.
My probably 32-gallon garbage can has NO brand name on it, somehow, but it looked just like some 45 gallon garbage cans with the Rubbermaid name on it. (Mine actually has a non-wrinkled area on the front with no name embossed there!)** I measured it with my arm, and theirs is a lot bigger than mine. The clerk thought they sold metal lids separately but only metal. But I have to find a store or website that sells the right size first.
But if you bought Rubbermaid separately recently, I'm on the right trail.
**A couple of my neigbhors have the same size. I'll have to go look if they have a brand name next garbage day. But they weren't around when my lid went missing. Their cans and lids were lying in their yards. I went out within an hour of the garbage collection. No one was around except the garbage men.... at least that I saw.