Unfortunately, you cannot simply get these items at any time due to your status as an unlimited founder.
The original black and white skull and crossbones bandana was released as a promotion of the new customization when clothing, jewelry and tattoos stores opened.
The red and gold skull and crossbones bandana was part of the 2008 founder's feast, and was only available during the time of the feast.
You can get the Kraken tattoo by beating Pirates of the Caribbean: Call of the Kraken however, check out the POTCO site for more info on that.
