You may have already spotted this thread on MG Experience, but Allen Bachelder (who owns a bunch of MGs out in Michigan) has one of the original sets of rear hatch louvers for an MGB/GT. He says he's going to take his apart and use it as a pattern to make reproductions for people who are interested.
This is one of those hens'-teeth parts that I've been hunting down for forever. If you want a set too, click the link above and let Allen know -- sounds like he's going to get started on the project this spring.