The table looks like pine, a very soft wood. You're overthinking this. Grab a can from the garage or the kitchen with the R you want, trace it on the corner with a pencil, rough out the cuts with a handsaw or a sabre saw, hit it with a belt or palm sander to clean it up, dress the edge top and bottom to match the factory roundover with a rasp and a sanding block. Done and done.
I did this butcher block using a paint can for my template. It's not perfect, but it doesn't have to be. No one would ever scrutinize it closely enough to ever notice.
