I never comment on shit like this, but I had to say this is literally the worst description and waste of a page ever. The site should literally fire whoever wrote this and hire people who can handle writing simple directions.
This is complete garbage.
For starters, there is literally no vendor where this map claims, not that the map is even remotely zoomed in or legible.
Next, I believe that the vendor that this article is referring to is Wilson, the vendor in V's Megabuilding, and the first ranged weapon vendor available in the game.
A little effort goes a long, long way, but a complete lack of effort will get you nowhere. I hope this site finds someone who isn't total trash to write future articles - not that I'll know, as I'm blacklisting this site for good.