Think a new prop is the way to go to be honest, if you do get the prop balanced you will lose a lot of thrust on the modified prop and there will be a risk of over revving at full throttle as the modified prop will present approximately half the load on the motor. Two bladed props that are meant to be so will have larger blade areas and a coarser pitch.
Don't know what the shipping would be to the states but it could be worth giving John at SOS a ring if you can't get one in the states.
If you have to proceed with the balancing the only thing I can suggest is some kind of static balancer similar to :
No idea if one for wheels would be sensitive enough for a prop though