Needs to be smaller. Think wearable with tiny PCB. So like SOT32 / 3x3mm DFN package
Yeah, this only comes in one package that will take about 5x7mm on PCB pads included. It's not huge either. Unfortunately, so far I haven't found anything similar in a smaller package.
Beware that this one is specifically made to monitor primary litihum cells. The BQ27220 mentioned by someone else, and many other such ICs, are made for Li-ion batteries only. This is not the same estimation algorithms at all. Maybe you can still use the latter if you set it up properly or only use a subset of its features, but that'll require reading datasheets very carefully.
The one reference I had otherwise in mind, which is *only* a "coulomb counter" and so would work pretty much with anything that's in the right voltage range is the LTC4150 that i've used before. But it draws too much current for your requirements, and is definitely not very accurate for small current draws.