AppleCare extends the coverage to 3 years, not 2.
It's good that there are companies selling the individual keys now.
What is also an option sometimes is to search for the individual keys, keyboards, or dead Macs at Ebay, Craigslist etc. Or even ask at a Genius Bar or a local service provider - both have sometimes keyboards that don't work but could be used for donating that one missing key.
And if anyone would ever have their Mac die, don't throw the keyboard (or other parts) away! It can save several Macs...