Rienzphotoz : A cheap one i found on the local Craigslist. It cost me about 15$. It's perfect for me as i've never had any issue. It must be an asian one, you might find plenty of them on ebay.
That's what you wanna buy if you juste want to try some Nikkors on your Canon.
Buy a regular Canon lens instead. The 17-40 will get you so much more for a decent investment and even better if you get it used or refurbished. If you need the 14mm all the time I would consider going for the Canon 14 L.
17mm is so different from 14mm. Have you ever tried both of them for giving that kind of advice ?
17mm is that wide. But 14 is ultra-wide.
A 14mm will give you shots that you'd never had been able to get from any other lens. The 17-40 is a trite and quite poor lens. It will just "make the job" when a real 14mm will give you astonishing shots. That lens is more than original.
On the other hand, the AF canon 14mm II is extremely expensive reported to the very occasional use you'll have of that focal lens. Second-hand Canon 14mm I are rare and stays expensive.
If you have 300$ and wanna have fun and a good IQ, the Samyang is perfect.