There are 3 Wolfe .44 pistols in this mission each with 18 bullets.
This means you can miss a total of 14 times and still get the achievement as it is a one hit kill even on 007 Classic difficulty.
The first can be found after Zukovsky is killed by returning to his office and looking on the small table in between the two sofas.
The second is found in the section of the club with waterfalls either side and 8 toilet cubicles. It can be found opening the second toilet door on the right next to some armour.
The third is found shortly after the kitchen. Rather than going through any of the doors into the club straight away you can go to the right and find a vent. Climb through the vent and you'll be taken to a new room with only one door to go through. Go through that door and you can find the last pistol on the right hand side on top of a shelf.
Make sure you aim down the sights for better accuracy and keep count of how many bullets you miss.
If you miss too many times (maybe 3-4) then you can reload your checkpoint and your killcount will stand as it did when you first got the checkpoint.