I can't remember where the discussion was but at one time I was seeking a venue where integrators could resell excess equipment on their shelves. I stumbled onto a Facebook group that apparently does just that and thought it might be of interest to IPVM integrator subscribers. They don't allow manufacturers or distributors to sell on the site " but I did see advertisements from some so not sure exactly how all that works. You'll need to check it out for yourselves. I just posted some Eagle Eye Networks equipment on it as a test run. It seems to work a little like OfferUp, was very easy to post and they claim over 800 group members so we'll see if my stuff sells.
The group is called "Security & Fire Buy or Sell" and the administrator is Al Columbo.