I have an item that's 3000 caps and I haven't been able to find any store that has that many caps.  Can someone please inform me which shop has the most caps?

There is a robot outside the gates of Gun Runners.  It usually has 8000 caps and some great weapons and a lot of ammo.  He will get 8000 caps every 72 hours or so.

Usually Gun Runners will have around 7000.

Thank you

This was the very problem I ran into when i wrapped the game on hardcore.  
 

" This was the very problem I ran into when i wrapped the game on hardcore.  
 

SPOILER WARNING: Click here to reveal hidden content.

After working the guard duty at Van Graff's (and following the subsequent explosion), I had all of these expensive weapons, but nobody to trade them with. I found myself for want of a nice market center like Rivet City in FO3.

"

I find the brotherhood Armourer also has a decent amount of caps, plus some high end weapons and armour.

The bartender at Mojave outpost also always has about 7k caps.