Contact Op-For Airsoft club.
They can help you out.
As for retail stores, other than PoCo Surplus and Warcraft Games I don't know of any stores that have a reliable supply. Daves Surplus occasionally does but I haven't been there in a long time.
A P90 will probably run you between $400-600. Depending on other accessories and such it can be sold for $800-1000 even (ie. charger, extra batteries, mags, optics etc.).
You're actually quite lucky with the new developments happening in Canada in regards to airsoft.
Where are you from? Did you play there before? And just out of curiosity what's your occupation? We have everyone from Engineers and IT people to students (which I am) to masters students to lawyers, to tradespeople, to police and governmental workers, everything.
If you have mechanical aptitude it definitely helps but isn't a requirement.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE