When checking amazon camera stuff make sure they will actually ship to Canada, lots of stuff only ship with-in the us. For a 50mm prime you have two choices, 1.
Pentax SMC-FA 50mm F1.4 (auto focus) or 2. any of the old manual focus 50mm primes. If you want auto focus get the FA 50mm but if you dont mind manual the M series 50mm's are probably one of the most populare. Search Henry's used section (warning, make sure your not buying a S/P lens from henrys used as I believe those are screwmounts and you would have to get a adapter for it), Craiglist, Kijiji and Ebay.
An FA lens is a lens made by pentax in their "FA" lineup. Theres also the K, M, A and others in the manual focus lines and FA, FA-J, DA and others in the auto focus lineups.
Enjoy!!
Thanks