Bigger shower waste rubber seal

[johnbroom]

I have recently dismantled and rebuilt my corner shower without problems apart from one. I have increased the height of the shower by 12mm but have not changed the plumbing which is a short 200mm spur to the waste pipe from the bath connecting to the external waste pipe.

The existing waste pipe is plastic with a 4mm rubber seal which goes under the shower tray. Above the shower tray is a plastic screw insert which seals itself to teh tray and the rubber seal beneath.

My only solution is to increase the thickness of the rubber seal to 17mm to allow for the additional height increase of the shower tray.

If anyone knows of an shop that sells such an item, please let me know.
The rubber seal needs to have an internal diameter of 50mm, external diameter of 75mm and thickness of 17mm.

[bobplum]

would it not be better just to replace the waste trap and the 200mm spur ?
if the waste piping is solvent weld this may cause a problem if so change to push fit piping