Furnished apts are a little harder to come by. Can you give a few more details that will help someone help you? What is your maximum distance from the center of Chambersburg? What is the maximum price range can you need to stay under? If it is for a short period of time and price is relatively flexible you might check out some of th motels in the area. Some, like the Travel Lodge on LWE, have excellent reputations and have a good restaurant on premises. There are other hotels or motels that specialize in weekly or monthly rentals , or will consider that if you ask.
If you are looking for something for a longer period of time you may find that renting or buying a few key pieces of furniture make more sense thatn paying theextra $$ for a furnished unit.
Good luck!