We've had this problem twice in 2 different vans.
On a previous Avondale Malvern we had it replaced under insurance because I believe it had been broken by something being dropped on it. The insurance disputed this at first but then agreed to cover it when I wrote in. The shower tray in that case doubled as the bathroom floor as they were combined. It didn't take too long to get this replacement if I remember correctly
In our present Avondale Landranger the shower had a doubtful looking repair in one corner. Campbells of Preston removed the tray and had it repaired pretty invisibly by their bodywork repairer. I was very pleased with this repair and it's still fine 4 years later. This was covered by the warranty we had bought with this secondhand van.
Hope you can get it sorted quickly
Sorry I don't know the cost in either case.
Best wishes
Tim