As I recall from your other threads, you are planning to use these panels in a portable setup. Not mounted to the roof, and not permanently out in the weather.
Why not just give the packing tape idea a shot, as time2roll suggested? Waterproof shouldn't be an issue if you set it out manually when needed, and yellowing will take a long time coming if it spends most of its time packed away.
Or maybe your portable plans have changed? Even if so, might be the best way to salvage this one for near zero cost.