I've been searching for a place in central Toronto to get frames powder coated for awhile now - I finally found a place and it turns out it's two doors further down the street from the place I work at. Here's the info in case anyone in the future is looking for the same thing.
Mayfair Plating - 96 Carlaw (Carlaw & Eastern). You can get there by the Queen streetcar (walk 2 blocks south from the Carlaw stop) or take one of the busses down from Pape Station.
If there's time tomorrow I'm going to head in and get some pricing info - It'll be posted here when I find out.