Where to buy trackpoint caps

I have a 2012 X1 Carbon Touch, and while I am mostly happy with the trackpoint, I would prefer to have the "soft rim" cap rather than the "soft dome". You can see the three types here: ThinkPad TrackPoint Cap Collection | Lenovo | (US)

When I bought a T400 nearly 5 years ago, it came with a variety of caps, but they are incompatible with the X1. So my questions are 1) where are the best prices for trackpoints caps, and 2) how do I know from an online listing if the cap will be compatible with my laptop?

 

Ebay. You should be able to find very affordable ones (how expensive should a tiny piece of rubber be?) and the product description will probably tell you if it is the right size for your device.

 

I was wrong about them being different sizes. When I was pulling the trackpoint cap off of my T400 it was also pulling off the plastic adapter that goes between the naked pointer stick and the rubber cap, which was making me think it was a different size. So hopefully there is only one trackpoint size to worry about for all the thinkpad models.

Ebay should work, but be careful in that there are 3rd party trackpoint caps that are sold that should probably be avoided.