Here are two options for searching junkyards;
www.car-part.com
EDEN Online - Hollander a Solera Company
I checked, and they both include Canada.
Depending on what transmission you're looking for, you can also keep an eye on various Subaru forums for people parting cars.
You can also check with guys like TomsSVX and SVXfiles, they usually have a few types sitting around ready to install...