I've had flickering when the capacitor on the points was on the way out. Didn't figure that out till it failed (shorted) and blew a fuse. Damn intermittent problems....

Most Auto shops will have the type that mounts with a screw.

A neat trick I learned for checking leads is to pop the bonnet in the dark and look for flashes. You can also just check the resistance of the lead. Or just swap them and see if the problem goes away.