About 18 months ago I could readily buy lithium AA cells but now the supply has all but dried up with only Eveready still selling the things. A couple of days ago I bought four rechargeable lithium AAs on Amazon. These come in a plastic case with a USB-A to 4 x USB-C adapter arrangement. Each cell has a USB-C port in the top and the fout-way tail cable allows all four to be charged at the same time from a single USB-A power supply.
They are rated at 1.5v and 2800 mAh, competing quite well with the 2750 mAh rating of 1.2v NiMh cells. I intend using them with the venerable 20+ year old Olympus digital camera that still works fine.