I left mine off. Not had any issues with water splashing up or clutch slippage but maybe I've been lucky.
Get a new one from vw on a trade discount if you are a good blagger. Should have some sort of gasket on it.
2 part numbers - 068103645M and - 038103645A but unsure of correct one.
The bolts that hold it are an odd size IIRC so part number: N 0102085