deskthority

Some of the IBM keyboards have a mouse pointer in the middle. The red cover gets hard and nasty after some time.
The replacement PN is 84G6537. It is the same one used on the Thinkpads.

Lenovo also sells the TrackPoint Cap Collection, which includes two of those, two of the "soft dome" caps used on ThinkPads since about 2003 or so, and two "soft rim" caps. And, if you like soft dome, they sell 10 packs of those.