As to the aluminum cover,Yes it can be difficult. I broke the first one I ever tried to remove, which is when I learned it was cast aluminum not steel. The last two covers that I removed, I used an adjustable wrench, and if it didn't rotate fairly easily, I didn't force it. I applied liberal PB blaster, let it soak for 30-60 minute, then applied heat with a propane torch, trying to heat the steel casting instead of the aluminum. Sometimes tapping lightly on the steel casting with a brass hammer helps while applying torque to the cover. If it doesn't come off, apply more PB blaster and lit it sit for another hour and repeat. after 3 or 4 heat and penetrating oil cycles, they usually loosen up.
I wouldn't recommend mapp gas or acetylene, as even with just a propane torch, you have to be careful not to melt the aluminum.
I don't believe anyone makes reproductions yet. I bought a replacement for one I broke by buying an entire original housing with the cover stuck on, and it was up to me to remove it without destroying it.
Brian