If you ask a hypothetical you can't really expect an answer, Arthur!
I have seen them come up occasionally over the years, although the chances of getting one when you want one seems quite slim, or you'd have to pay top whack. A rear diopter on its own compared to one as part of a rifle package is expensive, as you know.
Also, you need to make sure you buy a 75 sight that fits your rifle, since apparently there's at least two types:
http://www.network54.com/Forum/66438...ge/1442103945/