Looks like you need a blank transponder chip, found this:

“CUSTOMER LEARN” MODE This feature is only available on domestic vehicles or those which have a U.S. country code designator. This procedure requires access to at least two valid Sentry Keys. If two valid Sentry Keys are not available, Sentry Key programming will require the use of a DRB III® scan tool.
The steps required to program Sentry Keys with two valid Sentry Keys follows:

1. Obtain the blank Sentry Key(s) that need to be programmed. Cut the keys to match the ignition lock cylinder mechanical key codes.
2. Insert one of the two valid Sentry Keys into the ignition switch and turn the ignition switch to the ON position.
3. After the ignition switch has been in the ON position for longer than three seconds, but no more than fifteen seconds, cycle the ignition switch back to the OFF position. Replace the first valid Sentry Key in the ignition lock cylinder with the second valid Sentry Key and turn the ignition switch back to the ON position. The second valid Sentry Key must be inserted within 15 seconds of removing the first valid Sentry key.
4. About ten seconds after the completion of Step 3, the indicator light will start to flash and a single audible chime tone will sound to indicate that the system has entered the "Customer Learn" programming mode.
5. Within sixty seconds of entering the "Customer Learn" programming mode, turn the ignition switch to the OFF position, replace the valid Sentry Key with a blank Sentry Key transponder, and turn the ignition switch back to the ON position.
6. About ten seconds after the completion of Step 5, a single audible chime tone will sound and the indicator light will stop flashing and stay on solid for three seconds and then turn off to indicate that the blank Sentry Key has been successfully programmed. The SKIS will immediately exit the "Customer Learn" programming mode and the vehicle may be started using the newly programmed Sentry Key.

These steps must be completed in their entirety for each additional Sentry Key to be programmed. If any of the above steps are not completed in the given sequence, or within the allotted time, the SKIS will exit the "Customer Learn" programming mode and the programming will be unsuccessful. The SKIS will also automatically exit the "Customer Learn" programming mode if:

• It sees a non-blank Sentry Key when it should see a blank.
• If it has already programmed eight (8) valid Sentry Keys.
• If the ignition switch is turned to the OFF position for more than about fifty (50) seconds.

NOTE: If you attempt to start the vehicle while in “Customer Learn” mode (LED flashing), the vehicle will behave as though an invalid key is being used (i.e. the engine will stall after two (2) seconds of running). No faults will be logged.
NOTE: Once a Sentry Key has been programmed to a particular vehicle, it cannot be used on any other vehic