These aren't cheap but I'd recommend replacing the stock sealed beams with serviceable lights.
I have these on mine. They look like regular sealed beams but the bulb is able to be taken out and replaced. A lot brighter than the stock lights as well.
If money is tight and you want to just keep the sealed beams, the XJ takes 142x200 lights, standard square lights that several vehicles take, you can get them fairly cheap at most auto parts stores.