Fish forks range between 7-1/4 to 7-3/4 inches in length, generally falling in between the lengths of a flatware collection's salad fork and dinner fork. Fish forks typically have three, relatively-flat tines, which would ostensibly aid in picking up flaky layers of fish. Occasionally, a fish fork may have four tines and it entirely depends upon the manufacturer and the design of the flatware pattern. The outer left and right tines are sometimes wider than the middle tine(s) to provide leverage when cutting fish, although many manufacturers design their fish forks without the wider tines since often the fish course is eaten not only with a fish fork but a fish knife.
RestaurantSupply.com carries several fish fork patterns so you should be able to find an appropriate style to fit in nicely with your existing flatware. Be certain to match the stainless steel grade of the fish fork to your other flatware sets so they complement and don't look out of place.