You can now buy shorter version of the Rolex Oysterflex strap from Perfect Clones: "Special Short Asian Size". I comes with the clasp for around 75 USD. I am sure other TDs will be able to provide it. (Perfect Clones sells the watch with the short size strap, so you do not have to buy 2 straps).
I have a ca. 18 cm wrist and it fits perfectly. There are 3 adjustment positions on the clasp. I use the middle one.