Yes, with Steam games the version you receive depends on the version you activate. You can buy a key for $41 from the site Visualante linked to above (
https://www.gamekeysnow.com/keys/South-Park:-The-Stick-of-Truth), but as they're retail keys they're unlikely to come with the pre-order bonus pack. If you'd prefer the guarantee of a pre-order key, you can buy the game from
Nuuvem for an additional ~$1.70.
Edit: Do note that you may be required to use a VPN to activate a retail key pertaining to the uncensored version of the game.
Spotflux is free and US-based. Using a VPN is technically against the SSA but to date there are no verified or reputable reports of Valve taking issue with people using one to just activate a key or unlock a game early; indeed, myself and many other GAFers have used VPNs for these purposes many times over the years and haven't encountered any trouble whatsoever (the most recent example would be Thi4f, which first unlocked in some Asian countries).