Ugh...
What kind of projector are you planning on building? The parts required for the box will be easy to get from Rona or Home Depot. LCD monitors are common enough. You might be able to find a document projector (aka artograph) for sale at a flea market or something. They are good to salvage parts from like an 18" triplet or a front surface mirror, and even things like focusing mechanisms. Also, over-head projectors are quite common.
Basically from my experience so far, you can be industrious and mad scientist-like and try sourcing parts from junk lying around, or you can purchase stuff online, or do both (which is what most people do).
FS mirrors, reflectors, fresnels, bulbs, ballasts, triplets, lcds, can all be found *somewhere* in Canada but often it is simply more convenient to go to a known source for your shopping needs. I think ultimately it depends on how ambitious your build is. I think I'm one of the few Canadian members (or North American for that matter) that have purchased a 150W Powerball lamp made by Osram. Some things just aren't available here and must be special ordered and it is the law that you pay out your ass for it.
So far I have bought the following from the following places:
- Beseler Vu-Lyte II document projector with 18" triplet, FS mirror, and focus adjustment mechanism. Ebay for $40 Canadian plus $40 shipping. Shipped from USA.
- 10.6" LCD + Controller from Johnzo's Group Buy. $240 USD plus $74.52 in Brokerage Fees.

Shipped from Florida but the kit is actually from China.
- 150W Osram Powerball Ceramic Metal Halide. Model HCI-TS 150W 942 NDL. Bought this from commercial-lamps.co.uk from the UK. ~$100 CDN shipped. Ouch.
- Pro reflector from Lumenlab in the states. $20 USD shipped. Not bad.
- Condenser lens (x2) from Surplus Shed in the States. $18 USD for the pair of them shipped.
- Lumenlab FS Mirror from smartdude24. Bought off a fellow LL member in a brief in-person meeting. $20 CDN.
Still to buy: ballast, fresnels, Da-Lite High Power Screen (most likely from the States), and supplies for an enclosure.
Definitely check the trading post. You never know where these forum goers are lurking in RL (real life).
Don't be too afraid. It all depends on what you've got planned for a build. It *can* be put together for very cheap. However, it can also become quite the opposite.
Good luck.