aaacloseouts in New York are one, but they only sell by the truckload as well. Genco, as you have named here, is one of the bigger ones, if not the biggest.
RS Trading is one, Via Trading another and JD Closeouts. It really depends on the type of stock you are after as they don't all deal with the same companies.
I sell fashion loads mostly sourced through Macy's in Canada myself , and anyone can approach a company to buy surplus, no matter how big or small they are.
You will most likely need to show a line of credit, because they don't want to deal with time wasters looking for two or three cheap dressers. Each will usually have an MOQ quoter that you will have to take as well, however not all.