Both Amazon and Kobo will let you buy books in German from the Canadian versions of their stores. They may not have the full range of titles available, but if it's available in that language and not specifically geo-restricted, then Canadians can buy the books.
Here's an example: the translation of Elizabeth Chadwick's historical novel "Shadows and Strongholds", translated as
Die Erbin der Festung by Random House GmbH and available at both
Kobo and
Amazon for $7.59, which incidentally is cheaper in German than it is
in the original English.
Kobo does have the advantage that you will be paying in Canadian dollars and can currently use Chapters gift cards to pay for purchases and you can further discount their books with coupons if they are not from an Agency publisher (if a book listing has two prices in their catalogue, a List Price with a Our Price/You Save % value under it, you can use the coupons).
Unfortunately, they seem to have removed the category option for showing only books in a certain language and you will essentially have to know which title/author you want to buy before you can see if the German language of the book is available.
At Amazon, on the other hand, if you scroll down the left-hand sidebar of the Kindle Store page, then you use the Foreign Language Books link to browse through the German-language books. But their listings are cluttered by a lot of public domain titles you can get free at Project Gutenberg.
If you want an Amazon.de account so you can take advantage of the full range of available titles and any special deals they might offer, I'm afraid you're probably going to have to lie about your residence to them and use a German address, and possibly also a VPN proxy that gives you a German IP and pay with gift certificates from Amazon DE rather than your regular presumably Canadian credit card, just in case (sometimes Amazon demands proof of residence for people buying from outside the location indicated by their IP address if it consistently doesn't match their registered country).
Hope this helps, and welcome to MobileRead!