I’ve an old top box sat unused for years in my garage. A Maxia?? A bit bigger than 40l though, I think it’s 47litres. Takes one helmet. A bit battered and scratched but watertight and the locks all work. It’s got a back rest if you want that too. And it’s a monokey. The catch to flip the carrying handle is missing a bit so you need a small thin doodah to pop it out, and some of the reflective red trim is damaged. It all looks fine though. Free if you collect from Garstang.