Hi
for HV coil I am using Honda Transalp HV coil, on a Homelite 38 cc chainsaw engine, sorry only on a test stand , took a lot of abuse, no problems.
With this coil put in the air a Weedeater 18cc converted to CDI, small and low compression engine , but works, the only problems was the RFI, cured it and flown well.
But the Weedeater was very low in compression.
Any motorcycle HV coil will work, but must be CDI ignition.
Also experienced with the grey coil from a Echo 51 cc chainsaw, works , very small and light.This have two coils, magneto coil and HV coil (grey).
Good luck
Jose