Nothing is worst than checking your barbecue to see if its time to cook and you find out that your thermometer is broken. Then, you find out that your burners have been on max for quite some time (take that, gas bill).
To avoid those mishaps, just snag yourself a replacement thermometer. This guy is designed for Weber barbecues which featured side mounted control knobs. It is also made for the Master-Touch® and Performer® series of charcoal grills.