Look at the 3 digit number on the top. That tells you the ohms rating. For example, the unbroken one in the photo has 204. Thats 2-0-0000 ohms, so 200000, or 200K ohms. Then just find a pot that is the same size to fit where the broken one is and solder it in. Unfortunately, you'll need to know what it was adjusted to. I can't help you with that, you'll need to find a schematic or something. IF the broken one hasn't been accidentally changed from handling it, then you may be able to measure it with a DMM and adjust the new one to the same setting.
Thanks! The one that's broken has definitely been fiddled with (by me). I was seeing if there was a stopping point to the turns. It's supposed to be adjusted to 1.2V when it's in place.
