Where do I buy a buggy I've landed on a planet and I can't deploy a buggy because I don't think I've even got one since flown to several stations and

[GeneralIdea1964]

That's most likely the issue, only Equipment shown for the selected Class and below is displayed.
So clicking on a Class 1 Internal (too small to hold a Vehicle Hangar Bay) to browse the Equipment available at a Station will not display it.
So indeed, at minimum a Class 2 Optional Internal must be selected to Outfit.

Clicking on a Class 4 Internal or larger might display 2H, 2G, 4H and 4G Vehicle Hangar Bays, if the Station sells all Variants.

Yes, thanks for confirming falcon, a high tech should certainly stock them.
Now has OP got enough credits?
That's about the only thing left!