Can someone recommend a Coulomb counter to monitor 5V power banks?

I'm trying to test how long my project will last on a 5V USB power bank. Fortunately the power bank has a manual on/off switch so it won't shut off when the power draw is low. I'm trying to find out the overall power consumption say over a 24 hour period to gauge how long the power bank will last. I wonder if someone can give me a recommendation. Thanks.

Maybe you find something here which is equivalent:

Obviously it is would be a very simple matter if the power consumption was constant which I guess it isn’t in your case.

The YZXStudio ZY11266 is good;

https://lygte-info.dk/review/usbMeter%20YZXStudio%20ZY1266%20UK.html

Dunno if you can still get them, but the ZY1278 does much the same job and in colour.

Does the meter draw power from a separate source or through the same USB it is measuring?

It's not constant. It wakes up and takes a measurement, upload the data, within 25 seconds goes back to sleep the rest of 5 minutes before waking up again.

Now I have an idea. If instead I modify my code to just repeatedly reboot after each data point, then the power consumption would be more or less constant over time. If the battery is drained completely after x hours, then I can multiply x by about 10 when estimating the deep sleep battery drain because the whole thing almost draws no power when sleeping, or at least won't draw a few percents of the wake current. This should at least give me a decent ballpark estimate, whether I'm expecting weeks or months on that battery.

Artificially prolonging some of the short term activities during that 25 second time slot for long enough to get a measure of the current consumption with a standard multimeter could also work.
You could then measure the time it is in each of those activities in the original sketch by watching "something" on an oscilloscope/logic analyser.

The YZXStudio things take power from the USB port\supply they are connected to. They only monitor the current taken from USB device that is plugged into it.

OK I have something similar in color. I could run it on a USB charge to see if I can get a 24hr total energy consumption and then compare with charging a cell phone with the battery I'm using in my setup. I can assume the phone battery charging costs much higher power than the USB monitor does. This may work.