Since no one else is responding...
I'm no expert but I don't think there's anyone in Canada that offers what you'd ideally want.
The two most obvious choices are SpeakOut by 7-11 and Petro-Canada Mobility. They both offer unlimited
2G data in Canada for $10/month, however neither sell individual SIMs. You have to buy a phone to get the SIM. Also there are no 7-Eleven stores in Quebec so you can't buy account top-ups there.
There are Petro-Canada gas stations in Quebec and you can also buy top-ups online. See:
Petro-Canada Mobility Prepaid Cell Phone Plan
What to do? You might be able to find SIMs on eBay or even the Buy/Sell/Trade thread on
The Unofficial 7-Eleven Speak Out Wireless Canada Consumer Page. Make sure the SIM is for PCM, not SO. They're
not interchangeable.
Perhaps someone else knows if Rogers/Fido offers anything better.