First, does anyone know the name of the trim piece on the lift gate that houses the license plate light. On my ‘98 it’s a piece of plastic about 2’ long above the latch handle. Second, does anyone know where to get one?

 

Kind of referred to most time as a license plate light lamp cover.
You can find them on Ebay.
Yours painted to match or black like a bumper cap?
If painted to match sometimes you can find the color you need on Ebay.
Black like a bumper cap makes things easier.
But you need to be aware of a couple things.
There is more in there then just the cover.
Look at this diagram.

https://www.walmart.com/ip/Jeep-CHRY...6ZZZ/835192825

See how it is the cover itself, the light, and then the back?
So sometimes they are sold complete on Ebay. Sometimes just the cover.
Just the cover:

https://www.ebay.com/itm/27489907394...SABEgJUQfD_BwE

Oh and that is new and guessing aftermarket.
This looks to be OEM but still just the cover:

https://www.ebay.com/itm/32452912280...0AAOSwE8BgVMg1

The whole thing:

https://www.ebay.com/itm/28448739193...Condition=3000

But thinking this is a painted to match one for a black Jeep and not the kind that matches the bumper cap one.
There out there just take some work to find one.

 

Thanks Ralph. Mine’s black, should be easy.