Any VW dealer or auto parts jobber - ask for the air filter for a '79 Rabbit Diesel car. (Assuming you're talking about the rectangular element - about 4x12" or so)
Or, if you prefer, you could get one from Pathfinder in Montreal, but might be twice the price.
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)