Any ideas on how to repair a cracked Showed Wall?

Will87

We have a 2007 Lunar Goldstar and when we bought it in 2008 it had a cracked shower wall that the Dealer repaired by adding a whole new side and it looked like new. Since then another crack appeared on the back wall and we fixed it by using the clear tape.
This works really well and the crack hasn't increased but when we come to resell the van it isn't a satisfactory finish. Is there anyone out there that has managed to source new plastic interiors and repair the damage them selves?