I read on one forum that came up on a google search that Castrol put it back out as just Super Clean. Made sense since Super Clean is also in a purple bottle and is 2/3 of the name. So I go out to Ace Hardware and find the Super Clean but I couldn't find a Castrol logo on it at all. I bought it anyway to see if it would work, put it on and let it sit for about an hour or 2. It kinda worked and kinda didn't. It cleaned the hell out of the lens and took only a little bit of the paint on the back of it off.
I've also heard things like brake fluid, Pine Sol, and Easy Off oven cleaner. I'll probably try the Easy Off oven cleaner soon.