Hi Ken,
Having owned an EK and still owning an FE wagon, the rear side glass has always been a concern, especially finding good sets.
300 a pair is pricey, but understandably so. obviously the more you make, the less it costs as in all repro manufacture.
On the weekend, i went to the wrecker looking for seatbelts, and fortuitously found an FC wagon, missing the front and floor but with rear doors and glass, needless to say, the wagon is minus those bits now. glass was 20 bucks a piece (not perfect but able to be polished clean).
sometimes you just gotta be lucky ....
Cheers Ed