There's a lot of confusion and misunderstanding on the PPK's used in the various James Bond movies. I learned a lot when I wrote an article on The Guns of James Bond a couple years ago. Here's what I posted in another thread:
I wrote an article on The Guns of James Bond a couple years ago. The slideshow with the article has pictures of two or three actual guns used in the movies.
If you follow the links in the article you'll find higher res photos and more info on the various guns used in the movies.
The surprising thing is that Connery used a Walther PP, NOT a Walther PPK, in "Dr. No." The dialouge indicates it's a PPK, but the actual prop was the slightly largely PP. It was in 9mm Kurz (.380)
In other movies the various Bonds did use PPK's, in both 9mm Kurz (.380 ACP ) and 7.65mm (.32). They had a variety of grips including brown with Walther banner, black with no markings, etc.
Read the article and follow the links and you'll learn all you could ever want to know about the actual guns used. Then it's just a matter of finding one similar or a replica with the right features.
Btw, do NOT rely on the movie dialouge for what caliber the gun is supposed to be. There are times when someone says it's a "7.65mm PPK" when it's actually a 9mm Kurz prop or even a different gun altogether! (For instance, a Walther P5 is called a PPK at one point!)
EDIT: And in Skyfall it was a PPK/S with the supposed fingerprint recognition system.
http://www.examiner.com/article/a-look-at-the-guns-of-james-bond-for-the-skyfall-premiere