Seyco sells the Excalibur parts, and the blade clamp screws are the same on both. Also, you will eventually need the insert tips and replacement set screws, they do wear out.
In a pinch take any of the clamp screws to a hardware store with bins of screws, they usually have a place where you can try fitting your existing screw in until you find the right one, then you know the correct diameter and thread and can find more in the bins.