I use Protekto-Trim from Cowles Products (
www.cowlesproducts.com). It is part #37-831, 5/8" Black Band Molding. My friends and I have used this stuff on many XJ's. It looks great and lasts a very long time. It is the same trim I used on the XJ in my fender trimming article:
www.rocklizardfabrications.com/fender_trimming.htm.
I get it from a local auto detail and supply place here in town. I just purchased another kit from them last week and they just stocked up on it because we use it so much, so I know they have more if you want some. It comes in 30' rolls, and it takes about 22' to do all four corners, so you will have some extra just in case. It uses 3M adhesive, and sticks extremely well for a very long time. It costs just about $1 a foot (almost $30). Not cheap, but worth it.