This one doesn't cut it? https://www.foldnfly.com/2.html#The-Stable Granted, they fold the wings a really weird/ugly way. Also this variant for some reason: https://www.foldnfly.com/29.html#Lock-Bottom-Plane

That's not even the kind of lock I expected. It's possible to design a plane so once the wings are folded down, the fuselage is locked in a tightly folded position. I don't have a good online reference at the moment...