Alright, I've found the link to the list of all the NPC owned shops, but I keep getting a 404 error when I try to go there.

I'm looking for NPC shops were I can buy knives, packs, and belts and all that junk in Trax. Can anybody help me out?

Coincidentally I too just recently looked at that link while I was clearing out my bookmarks and it did't work so I deleted it. NPC shops are on Homeworlds... so if you find out where each species starts there is an NPC shop on that planet somewhere.
I can't really be more specific without hunting through every planet or race since I don't know off the top of my head.

Edit: It was only like 12 systems to look through so I did it anyway.
http://www.swcombine.com/rules/?Galaxy_Map&planetID=1990 Gand is a homeworld. Controlled by Alissma, so you should go ask them what city has the shop, oh and if they will let you down through the shields (or get there through NPC transit)

The answer to the shields is no, not for buying items.

And the shop is not in the starport city, so you'll be spending a while crossing terrain if you take NPC transport. (Unless Ellias gets around to talking to me about trading it with another 3x3 in the starport city.)

Well Hal, I'll be looking to making the entire NPC city NPC facilities when I get around to it.

But yeah, Shops are only on homeworlds. I'm slowly moving all the NPC stuff to one city, so if you land where the NPC starport is you may get lucky and hit one where the shop is in the same city.