Does anybody have a recommendation for lockable bindings for X-Country skis?

I was looking into these Serket ones, but I don't see how to order them and Serket does not return emails:
http://serketusa.com/patrol-ski-binding/

I would really like a binding with a lockable heel that works with normal footwear (so I can switch to snowshoes in certain terrain/snow conditions). I am starting to think I need to compromise on the normal footwear, but being able to lock the heel is a must.