I have also looked at getting curtains to keep pax in the back seat cool -but I have not found any either. I did get a chance to get into a cherokee that did have curtains and see how they did it. Homemade. Get out your sewing skills or spouse to measure and make them. They were supported by what looked like a cable or bungee cord sort of thing.
Got some Tan coloured material. Some spring bunge curtain lines with hook eye's which screw into the end. I used some self tapping screws with heads large enough to support the hooks.
Was a pain to make though as the windows are tapered. Make sure you make the space which rail goes through larger towards the larger end of the window as the curtains will jam on the rails as you draw them back otherwise. I made that mistake and had to remake them all grrrrr.
Looked good though. I've taken them down now though as a mate of mine said it looked like a caravan, since then I could never look at them the same again.
Don't overlook the fact that if You use "Any old material" it's not going to conform to regs, and as my insurance policy plainly states in all the fine print "Any aircraft found to have been repaired modified, etc using unapproved parts, materials, or proceedures is by definition deemed unairworthy in accordance with FAA regulations and is therefore not covered by this policy......Yada, Yada, Yada...
Buy Your material from an aircraft interior supplier (or treat it with fire retardent. This is more expensive, the retardent deteriorates over time, and on top of it all may be questionable in the eyes of the insurance underwriter.
