I bought the MZOO brand off of amazon and like it over the other brands I've tried. Taking a 20 minute nap in the late afternoon helps my late day productivity that it makes up for the 20 minute nap. My original intuition was that with my eyelids closed how much darker can it be to have an eye mask. The answer is: a lot. Put on this mask and close your eyes for a minute or two, then remove the mask while keeping your eyes closed. It is like someone is shining a flashlight on your face.

https://www.amazon.com/gp/product/B07KC5DWCC

These are inexpensive but they work well and I find the strap to be comfortable. The main differentiator vs some other brands is there is a big cup around the eyes. While sleeping (or trying to sleep) your eyes still dart around, and it is very distracting to have your eyelashes sweeping against a flat eye mask.

Another brand that is inexpensive and is even darker is from "Albatross Health New England". It completely removes even the small amount of light that leaks in, but it has to be worn tighter to get that seal. The main thing I don't like about it is when adjusted for my particular head size, the adjustment buckle is sitting right behind one of my ears and if I am on that side it is uncomfortable. But for $10 it is worth a try:

https://www.amazon.com/Adjustable-Blocking-Breathable-Comfor...