Recourse on used car purchased from dealership?

Anyone?

Ask the dealership you bought it from. Likely you are SOL, unless it was a CPO

There is no such thing as a "used car dealership".

Was it a dealership for a car manufacturer other than Volkswagen, or was it a plain used car dealer.

If the former, you should be able to at least have their service department confirm your diagnosis, maybe at your cost, and then proceed from there based on their reputation in the community.

If the latter, you don't have a lot to go on, other than stressing that the transaction was only a month ago. What's their BBB rating? Pay for a diagnosis from a VW dealer, and make your case.

Automotive dealers in Manitoba are probably self-regulated and you should make yourself familiar with what standards they have to adhere to.

This doesn't sound like a case where a used car dealer knowingly covered up a serious fault.

If you had a PPI done at the time of buying, would it have shown up a transmission fault code using a VW diagnostic computer?

Is it about time for a transmission fluid flush based on service history? Might be worth $200 or so to do that and see what if anything happens.

I think the best you can aim for is trying to get them to cover half the cost of the repair to keep their good name intact.
If they don't have a good name anyway, you may be out of luck.