Depth measuring tool

I saw this All Clad pan at Williams Sonoma that came with a depth measuring tool. Naturally, the tool is not sold separately. Does anyone know of something similar? I am constantly having to reduce sauces by half or more and in some cases precision is needed so eyeing it won't do.

I've used a bamboo skewer or "take-out" chopstick for that purpose. Just stick it in, mark the level if it's clear, and then you know how far you have to reduce it.