I have a small Ikea rug like this for Theo, but I have never used it. I would also consider getting this one even though it is an off white. It says it is easy to clean so if it gets dirty you would not have a large problem.
I will have to measure. I don't think I could cute and sew. Maybe I could be one of those small "samples" at a home improvement store? I think samples only cost a few dollars.