If you can buy just the valve, I'd replace it alone, rather than the whole canister. With any luck the canister shouldn't be damaged by the fuel saturation, as it is designed to hold fuel.

If you don't mind a little scrounging, maybe hit a local wrecking yard and see if you can find one that way? You could even get the canister as well, if you felt like it.
That being said, who knows where they hid the canister on your vehicle. Some of the new ones have been putting it on top of the fuel tank, or in that general area, making it more and more of an adventure to find.

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-Josh
Testing the cheap Mercedes axiom, one bolt at a time...