Yup, short barreled PS90's are available in Canada, restricted class. Long barrel is also available as non-restricted.
They are outstanding little firearms, funky feed design that is somehow very reliable, looks that would make a person on LSD question his habits, and enough Belgian engineering to tie both together.
Ammo is avalible if you keep an eye open, your best bet is to buy in the 1000 round cases when they are available, as they are the best price by far.
Expect to pay a minimum of $0.50 per cartridge.
Reloading has proven not to be the most cost effective option, as the firearms are blowback, the neck of the case stretches massively every firing, brass life for me is 2-3 reloads, barely worth the time, especially considering you can not tumble due to the specialized lacquer coated cases to make them feed properly in the magazine of the PS90.