For Ebay use, any of the older Nikon Coolpix models should work fine (for example, the Nikon Coolpix 990, 995, or 4500). The used market is probably your best bet.
But, lighting is probably going to be your biggest issue, and you'll want to use a tripod or other similar device so that you can stop down the aperture for greater depth of field (selecting a smaller aperture, represented by larger f/stop numbers in Av Mode).
Read through the posts in the other thread I posted a link to. It also touches onthis part of the solution (lighting), and also contains a link to a "canned" product designed for photographing small objects like jewelry if you don't want to try and make something yourself to diffuse the light better.