Easy question

[FFRDave]

What is the thread pitch and diameter for a Gas gas Motorcycle spark-plug?

Here is why I am asking.
I had a heck of a time threading my compression tester into the spark plug hole under my tank. I found myself wishing for an elbow of some sort that could act as a 90 degree adapter, so I could thread my tester on from the side.

I have decided that I can make one if I know what threads I need. All the adapters in my compression tester kit are streight, but of various sizes. Does anybody already already have one of these adapters, available for purchase
?

It may be as simple as going to a hardware store and buying a 90 degree plumbing fitting.

Its just an idea....