Greg, I'm not sure how far away you are from the American border (I think Ottawa is about an hour?), but what you can do is order products from the US and have them shipped to a Shipping Center just across the border. There are several that I can think of just in western BC, so I imagine there are many in the more heavily populated Ottawa/NY State area. For around 2 or 3 dollars, they'll call you when your package arrives and then hold it for you for up to a month. Then, whenever you have the time, you can drive down there and pick it up. From what I understand, it is perfectly legal to bring across hazardous finishing products as long as they are only for personal use, just so long as you claim them and pay the requisite taxes.
I haven't done this yet personally, but I know of others who have ordered products from ReRanch to these shipping centers quite successfully. It's quite a hassle having to drive across the border, but it's likely the only way to get a decent array of colors in nitro in Canada.
And Southpa, I actually live in Mill Bay, just up the highway from you in Victoria, and I've had some luck in finding refinishing supplies. You can get Deft nitro both locally and through mail order (Lee Valley). Also, you can get Mohawk products (I think they have a line of spray can nitrocellulose lacquer) from Slegg Lumber in Sooke or Sidney. They don't keep a stock of the products, but they'll be happy to order them in for you and you should have them within two weeks.
Or if you really want a selection of colors in nitro, you could do what I suggested to Greg above. It is quite a hassle given the time and expense of the ferry to Vancouver, but if you're ever planning to go to the mainland for another reason, you could probably make it work. There is a Shipping Center about 500m across the border in Point Roberts, so you can make a half hour detour off of the ferry in Tsawassen and then continue on your way.
What I've had absolutely no luck finding locally is grain filler. If you have a source, I'd love to hear it.
-Mark