Oil Leak from sensor above Coolant Flange

I have recently purchased a MK1 Golf Clipper. It is not without its faults but I don't think any of them are serious.
I have just replaced the rover cover gasket as it appeared to be letting a little oil out. I still have a leak coming from the sensor which is just above the water coolant flange on the right hand side of the block. Can anyone tell me where I can get this sensor from and how it seals into the block to prevent a leak. I can't seem to find any info on this? Thanks 

Any Ideas guys?

Try these guys http://www.vwspares.co.uk/g1switches.php

VW also sell the sensor last year, just make a note of what colour it is.
There is a little washer which seals the sensor to the head, there should be a new one with a new sensor.

Nice one! Thanks guys... Just what I need