Based on images of the X230T I can say that the digitizer is Wacom based. The included pen has: pressure sensitivity through the tip and the eraser, and has a right click button. The X230T conveniently has a pen holder where you can store the digitizer. While you may not be able to find a “X230T” or “X220T” pen you can find the same pen with the name of “X60 Tablet Digitizer Pen”, and this pen also fits in the X230T’s pen holder.
There are alternative pens, that may be even better. You can get a “Wacom penabled” pen (more info), which may feel better than the default digitizer. Another alternative is the Fujitsu Lifebook Digitizer, which has 2 buttons (more info). These other pens do NOT fit in the pen holder, but they do offer some extra features.
Note: Do NOT confuse the X230T’s pen (Wacom) with the ThinkPad Tablet pen (N-Trig). They are not compatible technologies.