Sorry, Phil. The last time I was in Builders Square/Home Quarters, I was pretty impressed with the wide variety of sizes that they had but I don't remember any specifics. I know that they had the ones for my daughters old house with no problem and they were relatively inexpensive. You might be able to order special sizes from a heating supply/sheet metal shop but I don't know for sure.
If you grills are in good shape, there is nothing wrong with reusing them. Since my daughter had standard sizes and a lot of paint build-up, I thought that it was cheaper and easier for them to replace. Every situation is different and even though I post a lot on a paint stripping board, I don't like to work if I don't have to. Certainly, in your situation, I would strip.