Rear Crankshaft Oil Seal?

I don't have the luxury of a workshop manual, so can I ask if anybody on here has ever replaced the aforementioned oil seal?
And does anybody have one in a part used gasket set that they no longer require please. Or at least a pointer of where I may get one for the 3 cylinder engine on a 'R' plate.
I have put up with a slight oil leak since owning 'noddy' for 3 years but it has now become not so slight a leak. So I am gonna have to get down and dirty with it.

Thanks in anticipation.

When you say rear, so you mean flywheel end or cam belt end?

Flywheel end.