i've found a couple of coils on some older echo saws that are the same as the zenoah coils. these were on the orange colored echos and i haven't seen them on the echo site and don't know if they were ever on the american market.
i've never seen the CH coil but at $20 i can't imagine finding a better deal if you have to buy something new. i think they mean that you (the buyer) has to pot the lead into the coil.
if you really want to tinker, you can try playing around with trigger-transformers like those found in strobes, flashes and stunguns. all these devices follow the same principals as cd ignition so be carefull!

zap...zap,dave