Hi there.
If you are looking for a darkbrown strap for you Laureus, I can recommen this one:
http://www.watchworx.co.uk/pages/lwb/elitePop/Explorer.htm
I know it's not croc, but it looks great, and wears perfect. I have one in this darkbrown for my Spitfire, and two in black for my Pilot and Laureus. They are great, and they are cheap! I have ordered them in 22mm, and they fit perfect! You can even put the IWC buckle on it.
The "best" part is, they smell of leather, and not of "plastic" like the ones that comes with the IWC watches! ;-)
I can recommen the 3717! Very nice watch :-)
Cheers,
Steffen :-)