I have a stained glas lamp in my bedroom that I love. I dropped it this morning (ok, actually I dropped a full laundry basket on it.... don't ask how I managed that ) the shade survived but I broke the screw that supports the thingie that the light bulbs screw into. I would assume you can buy a screw to replace it.... but where can I find that and how do I remove the old screw if the shank broke completely in half?

Does anybody know what I'm trying to describe happened to my lamp? I could photograph it but that doesn't tell the story any better.