Me and Backroads have seen em in BASE model XJs at the yard. In fact I snagged a vinyl rear seat that has the cargo area rubber included on the back of the rear seat.
There are companies that sell rubber for XJs... but from all the people I've talked to or READ from on here... these "made to fit" floors ARE NOT Molded to fit. you have to play with them. and allow them to settle into place. (heat helps)