It is a shame Lego has pieces like the 30288 blue panels and no trans yellow window for them. That's a waste of pieces for Classic Space building. Also blue frames like the 60596 and 2493 and no trans yellow windows. So when I found the ebay store, member 1974 mentions, I didn't doubt it for a second and also bought trans green windows for those old light gray frames.
This person only does flat windows, not curved windows nor pieces with studs, However even with these limitations, he has helped me greatly with my classic space MOC's here take a peek:
http://2kclassicspace.deviantart.com/art/MOC-Comunications-Outpost1-595504398
http://2kclassicspace.deviantart.com/art/MOC-Robot-Mobile-Centre-588313496
http://2kclassicspace.deviantart.com/art/Robot-Mobile-Centre-Transforming-1-608320086
Happy building.