Looking for DualShock 3 Screws

Hello. I just purchased a Dual Shock 3 from eBay and one of the screws on the back was missing. I went to a local hardware store and I was advised to go to a hobby shop because according to the owner, “no hardware store would carry those kinds of screws.” I would be very grateful if anyone would be able to direct me to an online purchase of the correct screws. Thank you.