You might look into the WonderPana system from Fotodiox if you're serious about putting a CPL filter on the Canon 14mm f/2.8 L II.

http://fotodioxpro.com/index.php/won...pl-filter.html

It's not necessarily cheap, but it's a unique system that allows you the freedom to use CPL/ND/Grad-ND filters with various wide-angle lenses.



Note: Just read some reviews on Amazon. Looks like the WonderPana system still shows some hard vignetting at 14mm. Also, CPL results just aren't good at that focal length (according to some reviewers).