[link|http://afterthemac.com|http://afterthemac.com] has one that'll run you about $56 USD total to have it shipped to Canada.
[link|http://www.macwireless.com|http://www.macwireless.com] has a 11b USB adapter, but they're rather proud of it - $99 before shipping charges.
I'm not familiar with either company.
On re-reading After The Mac, I suspect their adapter is an 11b adapter as well.