There is a great shop in Oshawa - I don't know how far this would be from where you are staying, however.
Ultimate Sewing Centre
191 Bloor Street East
Oshawa, Ontario, L1H 3M3
South of Highway 401, between Ritson Road and Simcoe Street at the 401 off ramp (in the No Frills Plaza).
www.ultimatesewing.com