that is a very good question! I looked just now and cannot seem to find it.
As I recall, it is the little bulb, itself, that gets replaced.
Though, if they have stopped making that particular shape, due to industry / tech change over the years, then the little socket might have to also get replaced along with whatever new type of bulb in it.
Here's what I did find:
The shift indicator bulb, and the ignition key "ring" illumination light, bulb is 90981-11014. Perhaps the same bulb?
Way back when I had to replace a few dash bulbs, I took them to my dealer and they provided them. In the internet era it isn't as easy to get that same level of direct service, and the parts diagrams available on the internet can sometimes be pretty rough, for small parts like this.