Codes expired years ago. PSN store page for the DLC is delisted.
No way to generate new codes. They were one-time use, tied to SKU/serial.
Used copies: Physical PS3 discs may have unused code in case (scratch-off). Buying used is a lottery.
Account Sharing: If a friend's PSN account has the DLC downloaded, you can activate their account as primary on your PS3 (Settings → Account Management → Activate as Your Primary PS3) → Download from their Download List. Requires trust.