Not sure what they're actually called, probably something silly like "fender support rods". I guess it depends on what you do with your Jeep, but their main function is to keep the fender from bending downward and separating from the body if you hit something, or if some idiot decides to use your fender as a chair. You could try calling the stealership, but you'd pay out the yingyang for it there. Next best thing is the local salvage yard, though around here there just aren't many Jeeps in salvage yards. Finally, you could just make one yourself. Get a piece of angle iron from Lowe's or some other similar place, put an appropriate bend in the end, drill a couple of holes and bolt it in. If there are brackets to hold it in place, you may be able to reuse them without bending the end of the angle iron, or you may be able to find something at the previously mentioned angle-iron-store that would work as a bracket.
Half the fun of working on a Jeep is getting creative when you can't find the exact part you're looking for.
