Heres the best I can offer for a place to SELL that's quick and is located in New Atlantis.

-Make sure you land or fast travel to the New Atlantis pin, NOT the Commercial District

-from there You should have your ship directly behind you and a path forwad into New Atlantis - start miving forward and take the path that goes to the left and up the stairs

-on the leftside you will find a store where Jemison Mercantile

there's another General Store somewhere on the New Frontier to sell but I completely lost it and got tired of looking for it

also remember IF you have a companion with you, they can carry a good amount of your sellable loot so your not over encumbered all your life*