It's a shame that you don't have the OT versions of Episodes 5 & 6 or the SE of Episode 4. I suppose it's a different narrator for the SE tracks than the one used for the OT track? If me bumping this thread means that more people will become interested and help you in your quest perhaps these tracks and the VHS version of Episode 1 can be found for you.
It's a shame that Episodes 2 & 3 weren't released on home video with the AD audio tracks. Were tracks for these two films created? I suppose to show theatrically? It's also a shame that WGBH hasn't responded to you at all.
By the way, I've sent you a PM.