Pretty Little Thing

I vowed that while I was unemployed, I would try to avoid trips to the craft store and work with what I have. Because I have a lot. This chain I bought when I was trying to figure out how to do the Six earrings, and I bought this leaf charm on sale (it's from the "Lost and Found" collection at JoAnn Fabrics).



My sewing desk project has been stalled by the need for a square head screwdriver. Do they sell such things at hardware stores? And how do you figure out what size you need? If anyone knows about square head screws (??) and how to extract them, please share!