Mendl are often quoted as a wide fitting, but I found them too narrow. My new pair are Zamberlain, fairly lightweight, totally comfortable and totally waterproof. I can't remember for sure, but I think the guy I bought them from said they do both a narrow and a wider fitting. I used our small local outdoor shop - they offered to stretch the boots slightly if needed - one of your shops may have the same facility.

Don't despair - good quality leather boots are still being made, and they are lighter nowadays than they used to be.