If you buy local and not from Warmoth it will probably be difficult to find nickel plated ones, so the best option is stainless steel ones that will be at Home Depot, Lowes, Ace, etc. Next time put a little beeswax or candle wax on the threads. Search for a screwdriver size that fits tight without any movement or slop in the phillips head. Usually easiest to find if you have the type that uses all the replaceable bits that readily available in the different sizes without having to buy a new screwdriver. Get someone to help you by putting lots of downward pressure on the handle while you slowly try to turn the handle. Also lay some rags around the plate and body with a tupperware lid etc. over the area in case you happen to slip you don't want a scratch or dent in the guitar body. If all else fails there are different tools and procedures to get it out, but try this first. The downward pressure is very needed though. Good luck and keep us posted.