I don't know the area but I found one at a wine making shop. Held grape juice.

Will the water be used for drinking or for the garden? I ask because you can get away with using "other" types of barrels for garden water.

I found this which so far is the closest but its still in Sudbury: http://rainbarrel.ca/ramseylake/ but you can also get rain barrels at Canadian Tire. If it is for the garden, you can use just about any plastic container. My mom used just very large totes.

There is always this for the really large stuff but it is in Southern Ontario and I don't know if they ship: http://www.dynamicplasticsolutions.com/products.php

why not go to a place that sells the plastic grey water systems and the big plastic holding tanks for farms? Septic tanks can be used for catchment purposes as well. Larger and relatively cheaper, I would get new ones over used ones, just saying. ;D

I think I read that septic tanks aren't designed for exposure to sunlight, probably the same for a lot of plastic containers, watch that.
I like the idea of 45 gal barrels. They're about the biggest you want to handle by hand. More capacity by adding barrels. And don't waste time trying to put a fitting in the bottom of the barrel. Flip it over so the threaded holes are on the bottom.
If you don't understand what I mean I can post a diagram for you.

Thank you to everyone who replied tonight.
Wilderness: I won't have the budget to buy the water catchment system brand new. But thank you for the thought!
Oldschool: The water will be used for the garden primarily, but I'd like to be able to use it for drinking as well if the SHTF. Thank you for the links.
Perfesser: Wine making! I never thought of that! Thanks! I completely understand what you mean about the threaded holes. (Thank goodness for initial research on YouTube!)

if you P. M me i live close to Parry Sound .moved here from S/W Ontario ,and have a great soursce for blue food gradge barrels.....logger1