I'm still waiting to buy a mechanical keyboard with a TrackPoint. Until then, the ThinkPad external USB keyboard [1] is perfect. Its big delete key is great, too.
I've got two old Model M 13s with trackpoints. Unfortunately, the buttons on one of them are failing. I never realized how much I used the trackpoints till they didn't work.
[1] http://shop.lenovo.com/us/en/itemdetails/55Y9003/460/60AC6A0...