Diff lock actuators: anyone has repaired the small rubber boot yet ?

[Louis-Alain Richard]

Both diff lock actuators (857 711 995A) on my car suffer from a leak at
the little rubber boot. The diaphragm is OK, as well as the plastic body
and both vacuum nipples. Audi wants 255$ for each one. 

So anyone has an idea how can we re-seal the plunger with the body ? 

The OEM setup is a very thin and supple rubber boot that slips over a
15mm plastic tube at one end, to a 3mm shaft at the other end. Overall
length is 30mm. The stroke of the plunger is 20mm, so the small end fits
into the big end when compressed. 

What we need is a "shrink tube"-like material that keeps its suppleness
over and extended temperature range. 

Any ideas ?

Louis-Alain
Preparing for the winter...