Hi, I have a used CDI Electronics 511-9766 Spark Tester. Please reach out with any questions. Description from CDI website is:

Enclosed 8 Cyl., adjustable spark gap tester. Has heavy-duty wire for mounting in any position. Helps reduce possibility of igniting gas fumes Adjust from 1/8 in, 1/4 in, 3/8 in and 1/2 in. Requires you to use your existing Spark Plug wires