With a system that's on the order of 20 years old, you have to buy what you can find - there's not much of a market for batteries for this system, so it's take what you can get.  Chances are just about everything you can find will be pretty old.  
I’ve got this old Latitude CS 400Xt that I bought new years ago. It still works fine, I need a new battery for it. I can’t get rid of it as it has programs on it that won’t run on newer OS, like an eprom programmer, car diagnostic software, control system program, etc. I’ve looked for batteries on line and they all seem to be the ones from the other side of the world that claim to be either refurbished or more powerful than the original. I’ve bought batteries from places like this in the past and they just don’t last. Anybody have any info to help me out? Thanks in advance.
Latitude CS 400XT High Capacity Battery p/n 8012P 14.8 volts 3100 ma