Print Walther PPK LEFT and right from http://www.thingiverse.com/thing:19158
Glue left and right together
Print WALTHER PPK Silencer
Drill out The Walther PPK gun at the barrel with a 7mm drill bit
Add 8mm threaded rod in Walther PPK Silencer and tighten down. (optional Glue it in)
Tap or screw in the other side of the threaded rod into the gun.
Paint rod to match silencer
Enjoy being James