You can buy a used fob off eBay and use the GAP tool to reprogram it work with your truck. Make sure it's the same type as your existing one.
HOWEVER: You will need to buy the metal key separately, either from the dealer ($70, IIRC?), or buy a blank off eBay and have a local locksmith copy your existing one (~$35)- assuming it isn't lost.
Also, the used/reprogrammed fob will only work with good batteries in it. If the fob batteries are dead, you can't hold it under the dash to start the engine like you can with new/dealer-sourced fobs.