On the Phelps, I have a 20x20 Bomar hatch. the glass (?) looks like tempered glass when it's impacted, all crazed. Is an impending failure or are they safe looking like that?
If you use urethane windshield goop, it bonds the 2 together such that the windshield is considered to be a part of the structure on the car for safety standards. I am told it can also restore human life, repair a broken hymen and a broken heart too.
Replacing the whole unit with the same size is not a very big deal. Some screws and cutting through the old sealant. Take your time to prep the surface well before installing the new unit.
I think just trying to replace the lid sounds like a disaster waiting to happen.
I have no idea if going to a larger hatch is possible in your application.