Who in my area (Stratford, Ontario) can replace the gas in my double pane window and re-seal it?

Answer 1

The answer is NO ONE. The gas leaked out through a crack in the seal that may not be visible until the window is removed from the house. Even if they found the leak (and it might be so small as to be unfindable within any reasonable time) they would need to have a manufacturing facility that could reseal it.

You would be better off from the point of time and money spent to just get a replacement one, sealed at the factory, and with a warranty.

Answer 2

if the seal is broken and or shot, the only thing you can do is replace the window glass. you cannot re seal it.