I don't know about Canada, but American Yamaha stopped importing the XT600 in 1995. The question is ... will sprockets from '95 work on your 2003?
Unless substantial change has been made to the XT since '95, then I'd guess a '95 (or earlier) sprockets would work. Try the ON LINE dealers, find best deal. There are dozens of Yamaha dealers nationwide. (remember, Yamaha dealers in ALL 50 states ... probably about 1200 dealers total but not all on line)
The other problem is MOST Japanese OEM's support a model for 20 years ... so you're right on the edge. But there still may be stocks available somewhere. Dunno?
Also, if you scour the after market parts world, you may find non OEM sprockets to work as well.
Try JT, they are pretty good. (Beware no name Chinese sprockets)
Also good: Renthal, Sunstar, PBI. But OEM are best, with JT right behind.
Any chain of the correct pitch (520 I assume?) will work fine ... but If I were you I'd spend some $money$ and get a high quality chain, like a DID 520, X ring. This available nearly anywhere.
DID 520VX2 X-Ring Chain - Motorcycle Superstore
Count links in your chain or check owners manual, buy a chain of equal length or longer, then cut to length, which is Child's play with correct tool. Use a Rivet Link if your serious about your chain staying on.
2 minute search found this:
1995 Yamaha XT600 XT600EG Sprockets - BikeBandit.com