Sterling Eccles Rear light lens

Triumphantwoody

I have a 1998 Eccles. It is our first caravan  The rear light  lens is held in with 4 bolts. I tried to get them out but they just swiveled around. I drilled the heads off but in the process the lens cover, which was 17 years old, had become brittle and
broke away. The bolts are held in with rubber grommets that lock into the fibreglass shell. There seems no way to get to the rear of the housing and the damaged grommets just fall ino the void behind. Can I get new grommets? Is there a better way to secure
the lens cover and lights?