I've just had some canvas posters done up at PosterJack. Good quality and a Canadian site. I might have a referral code too. They also seem to have frequent sales...36x24 canvases might be on sale right now too.
For smaller prints have you thought of just using your own printer? I print a bunch of stuff on my photo printer at home and get good results. They are all going to fade overtime but you can just reprint easily if necessary. Ink cartridges are cheap off ebay or Amazon.
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