In any very specialized field you have to have patience as there are only so many opportunities at any given time. you may find you need to look for a few part-time positions at multiple places.
Many Dry Cleaners have an alteration services that employees independent people for work.
Also some men's clothing retailers will have alteration services - companies like Moores, or department stores like Sears or The Bay.
Doing alterations may not be your ultimate goal, but it may be a way of getting you some early employment.
Refer to this link to get some more insight on Canadian job search strategies:
http://careego.com/CareerResources/ImmigrationJobSearch/JobSearchStrategies/tabid/325/language/en-CA/Default.aspx