You are correct with your belief that you don't sell this type of lead, nor should you. Actually it would be an adapter that surrounds the coil for secondary then a pickup would be placed on it. There is actually no need for such an item that I'm aware of since primary is mirror of secondary. Certainly these are produced, but have little value for diagnosis.
If our guest would like to discuss this further, I will honor that.
Good point Carl. You can view the spark line characteristics looking at the primary voltage.
However, several COP models have the coil driver inside the coil. On these type, you cannot ever look at primary voltage. So, if you do want to see the spark line for combustion analysis or whatever, you will need some method of picking up the secondary.
A very effective pickup can often be fashioned out of a bit if tinfoil:
I wasn't aware of many COP systems that primary voltage wasn't accessible except some IDI or Cassette units. However, the secondary on these can be accessed via HT jumper leads. GM CNP primary isn't available, but of coarse secondary is.
Hmmm. Nissan comes to mind, Carl. 1995 Maxima 3.0 COP is a good example (at least the US flavor). The coils have three wires. Power, ground. and IC. The power transistor drivers are inside the coils so primary voltage access is completely impossible.
Some Toyota/Lexus also have the igniters inside the coils.
Good luck with your project. Is there anything in particular you are interested in with COP ignition? Do you need manufacture specific data or would general be ok? If you could give us an outline of your goals, that would be helpful.