Take the cleat down to your local hardware store, ask them to match it up. It's most likely metric. Try to get stainless. I manage the hardware department of a True Value and had a guy bring in his Speedplay cleat the other day looking for the screws that fell out. Easy peasy. Don't go to Menards/Lowe's/Home Depot, most likely won't have them or will have to buy in a bag of 10 or something.