RS Components is your best bet for them.
I cant remember what they are called, there was a thread on the kingman boards i put up, but they have just upgraded and lost all the threads.
You could search these forums, as im sure i posted it in a spyder thread here too.
ODE - If its sort of tripping, but not with enough power to trip the sear all the time, then it prolly is the capacitor, it seems to be a problem with kingman boards that the soldering is crap.