Oil System Purge Push Gauge

Changing all my oil lines etc. as a part of the five year rubber replacement, so I’ll need to do the hydraulic valve tappet check after I purge. What push force gauge are folks using to measure the 16 pounds of force required? The manuals state something like a fan belt tester can be used. Searching online, every gauge I can find for belts tests only to 10 ft. lbs. and the other gauges I can find that should work are quite expensive for something I may only need once every five years.