I recently changed my propellers and by the very simple and basic photo a to a and b to b guide i was given, apparently some of the props didn't stay on as I tried to take off. In the process I lost 2 of the new props but the big issue i have is the screws for those 2 and the other 2 that I was able to recover were gone in the grass somewhere. Anyone know what type and size screws these are, and where to purchase them?