Where can you find replacement brackets for the overhead canopy of a 3-seat outdoor patio swing?

That's easy. Your best bet is Swingcushioncovers. They make all styles of canopies for the outdoor patio swing and they use Sunbrella fabric so it won't fall apart in a few years like the original fabric.

Gardenwinds is also a good choice. They guarantee a fit or your money back! They also use a fabric that is 30% thicker than the manufacturer's original.