Equipment seems to be random. I went to a station. Docked, saw there was nothing I wanted, when the game crashed. Restarted and the stuff I wanted was there.
I imagine it is like the upgrades in Frontier: equipment availability varies by the tech-level of the system, coupled with a general demand/availability factor, allegiance, etc.
I'm still early days with only a couple of k in credits, but when I look at the equipment nothing is listed. I understand that I can't afford anything, but why not list it? I would like to know what to aim for and how much I need to make.