Although Rocket Fins are not prefered in the DIR diving community (we prefer Scubapro Jet Fins), most divers have replaced their rubber straps with SS springs - which can fit on Rocket Fins. I am not sure if they are advisable for military applications, but I do know that several well known technical divers (Jarrod Jablonski to name one) do use them.
They are not cheap, and can be a PITA to install, but once done, they never need replacing. You can check them out here:
http://www.spring-straps.com/
This is one site, but there are many others. Just remember that when you install them, make sure you place a piece of rope in the spring so that you do not over stretch them. I hope this helps.