Ed, you can tell us...was it a gator that got the fin?
Jerry uses Future's fins. I'm sure that he can get you replacement fins. The base of the fin will have the style and size molded in - something like SB3 or G1 is the style and I do believe the depth will be molded in too something like 400 is a 4" fin. The size can also easily be determined by measuring from the top of the base to the tip - IF it was one of the side bites that was broken, measure the good one.
If the trailer was destroyed and there is no base left in the board, you'll probably want to check with Jerry to see what size he used in your board, I have seen most of the recent SS's with 3.25" trailers.
If you need the fin ASAP, no doubt you can find something at a local Ron Jon down your way.