A lot of Limiteds came with them. Some Country, Briarwood, etc as well - basically any of the luxury editions. It's pretty easy to find them though, just walk down the row of XJs at the yard sticking your head in each one.
What you need to complete a full OEM-quality install:
* front and rear brackets for mounting to the ceiling, plus all screws (but they're just 3/8" long #8 self tappers, as I recall)
* the overhead console itself
* the wiring harness from the right-hand A-pillar on the donor
* the temp sensor and bracket - held down by the same bolt holding the center bottom edge of the header panel, right behind the bumper
* the extension cable from the sensor back to the connector under the front of the PDC.
I believe anything from a 90/91 all the way through a 96 will be "plug in and go" - at least if you have power windows, power locks, or power mirrors. If you don't have those, your cross-body wiring harness (the one that goes across the floorboards under the carpet where your feet go) may only have the wiring for the door speakers. You may run into slight differences on the two pin connector under the PDC for the temp sensor, but it's just a thermistor so if the connectors don't mate properly, clip the connectors off and use some crimp splice terminals. Just make sure the wire colors match - they should be black/light-blue and green/purple (or purple/green, I forget.)
If you install it and your temp display shows SC or OC, you have a wiring fault - SC indicates a short circuit and OC indicates an open circuit.
EDIT: when pulling one at the yard, don't just yank down after unscrewing. Removing them without breakage is easy, unscrew the screw at the front, slide back about an inch or two (might take a little muscle but not much) drop the front end down, slide it forward and wiggle a bit to unclip the rear bracket. Also, expect the retention clips holding the wiring harness to the A-pillars and leading edge of the roof to be annoying to get out, don't sweat it too much because they are only needed till you get the trim back on. If you don't have lighted mirrors on your sun visors and don't want to ever retrofit those as well, you can simply clip off the annoying long pink wires leading to the connectors for those instead of trying to detach them from the ceiling.
