For those still hunting one, there is a pre rail 4513TSW up for sale on the Guns International auction board. Looks to be in good shape, 1 mag, $499.
There also is a 4553TSW listed in the classifieds here. Hope this helps!
As far as duplicates or spares go, I sold every one of mine EXCEPT the pristine 4513TSW back up to my Pre rail 4513TSW EDC. Neither of those guns is going anywhere.
Regards 18DAI