Your price range of course will determine what you can buy, and what millage is on it. Since I have been looking for a diesel out in Ontario for the last little while I have been checking and keeping an eye on the usual sources of places.
www.autotrader.ca Put in Volkswagen as make, and place the years and price range and be ready to look through a bunch of ads(Stupid site took out the option of allowing you to put a keyword as well). I have seen a few cars under the $3000, 1 jetta and a golf I think, but again keep looking and you never know. Another place to check is
www.buysell.com and just type diesel in the search and click on the categories that intrest you. Last but not lease,
http://toronto.craigslist.org/ Sometimes stuff comes up, sometimes not, just keep an eye out for stuff and you could get lucky. Hope this helps, I bought a 93 jetta with km340000 for $2000 over a year ago and the thing has worked good for the torture I put it through (Food delivery, and Toronto driving, not a good combo) so you never know what you could find!
Benjamin