You need new blades or just the screw. I have the screws they are about $1, I could mail one for 60c. The best way I have found to get them out is
A: Take a dremel and cut a slot across, doesn't matter if you cut the shaft a bit, and unscrew it with a small slotted screwdriver.
B: Heat up a screw driver with a torch or gas stove and when it is glowing red jab it into the screw and then the plastic will harden back up stuck to it and you can unscrew it. Only do this if you have some small screwdriiver you don't care about because odds are pretty good you will ruin them, and be careful not to get burned. I only add this if you don't have a dremel.