There used to be a boat propeller shop near Argyll on 91 Street, Edmonton, next to where I worked. It's closed for several years now. I took an aluminum door top to them, and they did a good job. That was fairly thick material.
I had a tear in the bottom of my 110 tub, and took that to Jet Craft here in Grande Prairie, a boat manufacturer. They did good work as well. The welding shops here do TIG weld aluminum. They may charge more than the boat shops though, or be less experienced with thin aluminum work; I don't know.