This mod replaces John Wick's shades with Mr. Foster's gasmask from Tripwire Interactive's game Killing Floor. It includes an adapted model, the original texture from Killing Floor, and a custom normal map. Personally, I think it looks pretty good!
You should install this on top of Wobin Ralker's awesome Mr. Foster mod (which also includes some of my other mods, such as Mr Foster's suit).

Q&A
Why does his head look fat and deformed?
I had to modify it to fit over Wick/Foster's head and hair, to avoid clipping. I may improve it in the future!
In game, Foster is still called John Wick and he puts the gasmask on like a pair of sunglasses!
This is an issue with BLT, I think. It shouldn't happen after version TWO, but if it does, you may be able to fix it by navigation to your PAYDAY 2/mods folder and renaming the folder called "Mr. Foster" to "Mr Foster" (with no .). If that doesn't fix it, make sure you do actually have Payday 2 BLT or BLT: Club Sandwich Edition.

Changelog
TWO
I rounded out the gasmask so it looks less deformed and just looks a bit large. I also subdivided the main part of the gasmask for some delicious smoothness.
ONE
Replaced Wick's shades with Foster's gasmask.

Thanks to I am not a spy for releasing the Diesel model tool! Good luck to him in his future endeavours.