Well searching for why the Kindle Fire didn't seem to be available in Canada I came across these pages:
Link 1This one is a bit technicalI can't find anything saying that the Fire is unavailable in Canada so it may just be sold out. The Kindle Voyager, their top end reader, tablet seems to be sold out in the US and Canada. Since your husband would not start out with a US account but have a Canadian account in the first place he would not be affected by the problems mentioned in that first link. But it seems that some books may not be available in Amazon.ca because of quirks in Canadian law.
The only other reader that I am familiar with is the Barnes and Noble device, the Nook. And so far as I know B&N has not updated that reader in years. I know that using B&N is a lot more difficult than using Amazon. Someone gave me a gift certificate for B&N last year and it took me an hour or more to buy a book from them. On Amazon buying happens in a second or so and the book shows up on your reader in a few seconds.