This inexpensive coil works for Energy Transfer ignitions. Emgo part #24-71532 "Universal Coil for both 6V and 12V Points or CDI". I got one for $15. It is made in India but appears well made.
I had to make a small bracket - easy - just a short 1" x 1/8" flat strap ( I did not want drill a new hole in the original ET coil mount brkt but you could). I used a short jumper - white wire in picture (because I didn't want to cut my original wire harness to change terminal ends). And it needed a longer high tension lead - just twist out the wire and twist in your own.
Whether it is better to spend money on the ET system or convert to 12 volts is your decision. At this time it was easier for me to just change the coil. The bike starts and runs great now.
I know this was a topic of discussion here a while back. I posted this on cubsite.com also. Hope this is informative. Al.