While I have a Casio FX-991ES at hand, I found myself using a smartphone instead.
Bigger buttons, bigger numbers, has backlight, and if you don't like the calculator app's look, install another one. Can have more than one calculator at once, and smartphones are usually smaller and flatter than a pocket calculator.
Plus, even the out-of-use 10+ years old smartphones have many extra features useful in the lab:
- camera
- flashlight
- chronometers/timers
- WiFi, BT
- mp3 player/radio
- voice notes
- the big screen ones are great to display a schematic or a datasheet, etc.
I always keep 1-2 smartphones (without SIM) somewhere on the workbench.