Zv said:
I opted for the Samyang 14mm f/2.8 instead as I got fed up waiting. It's a pity I can't use filters with it though. Blasted bulbous ends! Haha!
Actually, there is a (very expensive) Hitech Lucroit Filter Holder. It was originally designed for the Nikon 14-24, but they made adapter rings for other lenses, including the Samyang. It can be found on their site and places like B&H, Adorama, & Amazon. You'll also probably need to buy new large, expensive filters to go with it of course.
http://lucroit.com/SHOP/category.php?id_category=5
Also I believe Samyang posted something on their FB page about working on their own filter holder for it. As I recall they were hoping to release it around now.
There are also a number of home-made filter holders I've seen, you can google them and see if they look like something you'd like to try to duplicate.