Have you tried Foden themselves? They built quite a lot of 2-strokes for a variety of applications. The 2-strokes were still being fitted to trucks, usually cement mixers, well into the 1970s. I think they were killed off by the noise regs: their unmistakable banshee scream was just too much. In my area, my first port of call would be an old established outfit called Pistons & Components (in Glasgow) who can generally be depended on to get hold of any engine gaskets/bearings/pistons/rings still in existence.
