the coils i dug out of old 3W ignitions and also hand wound a couple of copies. these are about 12mm diameter x 14mm long and weigh nothing. the primary is wound directly on the ferrite rod core and stuffed into the secondary's bobbin which is a six layer stack. no insulation between the secondary windings. basically a standard trigger coil with 100:1 ratio

the main cap in the 3W is rated at 250 volts so i doubt their converter is putting out more than 200. have you tried the CH coil on less voltage?

dave