Hi, Parker. I have to confess that I have never seen a pocket door for an exterior application and that is essentially what you want. A pocket door would not seal well enough to do much good for what you are considering. Sounds to me though that you could take aout a little bit of wall and install a sliding patio door that might be closer to your needs.
But for the real expert guidence in this area, you best ally is probably the people in your local building code enforcement office. They know exactly what they require and can probably tell you where to get it.
For what it's worth, I know someone who did a real "Old House" project in your area. He rebuild an old carriage house in Mississauga into a beautiful house. He moved back to the States 20 years ago though so he would not be much help to you now.