I've been using ebay for the last few years, with paypal.
you can find more details on many topics here-
I've bought shoes, greenhouse , lots of old car parts, baby stuff...
Just price check, and ask questions if you aren't sure about an item.
I always set my searches for USA only, and often top rated sellers & returns accepted.
you usually will have to pay the shipping when doing a return, but I've never had any issues with getting the money I paid for an item refunded.