I'D try the local ford dealer..bet it costs next to nothing.

my mk3 used to let water into the car whe it rained, ie when i braked water would flood out of the rear high level brake light onto the rear seats...nice...

the rear jet washer sits just above the high level brake light...theres no nuts or washers holding in the washer nozel it just clips into the boot metalwork. i fixed the leak by removing the jet and smearing silicon around the base and re-assembly...

reson i said try ford dealer for a new rear jet was at the time I had orange side indicators on my mk3 and want clear ones, after market car shops where selling them for about £25 a pair....then i notice a st220 in the showroom with clear ones ....tried the main dealer parts dept, and hey ho there half the price of the aftermarket ones and they fit....unlike the naff aftermarket stuff that rarly does...

best wishes paul.....