Running the Prime with AAA batteries

[Stefan]

Nice one! And good to see that you did not have to sacrifice your (or mine ) calc.

If you intend to run it for a longer time of batteries (not just for measuring) you maybe should consider using a switching regulator. Otherwise you burn most of the energy in the LDO.
I know that TI (I guess other manufacturers have similar devices) makes some regulators which are pretty much drop in devices, they even include the inductor already. Look for their "Simple Switcher" series. Maybe you even want to use the "Nano" ones to fit everything in the battery adapter.

And then you can print a battery cover