There are a couple aluminum shops near me that do welding on just about anything, boats aren't their specialty but repairing and fabricating aluminum is their bread and butter. If you google search Aluminum welding in your area you will find someone that could get you fixed up. They will most likely have the material instock for the repair. You would be responsible for paint and applying sealant yourself unless you dealt with a boat repair shop that would cost you more than double. Depending on what gauge your boat is will determine on how easy it will be to repair. Some tins that are thin skinned, like .06 and under can have blow through. Be sure there aren't any other options before you cut and replace. I would expect it to cost no more than $100, but I would expect to have to apply sealant afterwards.
