First, its possible inside your computer case, there is just a loose cable that is causing the problem with the front jacks on your computer. Check inside, right behind where the earphone jack is for a cord running to somewhere on your motherboard or Sound card.
If that dosn't work,
Do you have a CD/DVD player with a earphone jack and have you tried that?
Assuming its the port that is bad itself and not just loose, you could check in at radio shack, bestbuy, or newegg.com for a cord that splits the output. If you get lucky you might find one with a chanel select that will allow you to swap which recieves the output.
The other option, from radio shack I got a Bluetooth USB adapter for $20 and a good pair of BT earphones, again purchased online for cheap (I recommend samsung BT500 earphones).
Another alternative, my speakers have a earphone jack in them as well (the computer speakers, as well as the reciever I currently have my sound card plugged into).
If you have a quality home theater set up, for $80 on new egg you can pick up a good soundcard with optical, Coax, and AV out which you plug into your home entertainment center that again will allow you to use headphones.
Good Luck