scupper plugs

Hi new to this website.anyone know what size scupper plugs would fit a Mainstream Kingfisher?

No Clue, But
Try and measure the hole and get drain stoppers from the hardware store. Buy one, and if it works, buy a set

Try some foam Golf balls…

scupper plugs
You can buy these at marine stores in various sizes. They have a pull chain or rope built in. If they don’t fit you can easily trim them to size.

Big Mac