Reddit mentions of Icstation Mini DC to DC Voltage Regulator Step Up Boost Converter Power Supply Module 1V-5V to 5V 500mA (Pack of 5)

Lithium batteries will be 4.2v fully charged and down to around 3.3v on the low end. You can easily power 3.3v modules like the Pro Mini 3.3v off the battery itself.

If you need 5v or higher, you can use a boost converter. I picked up these recent, but haven’t put them in a project yet: https://www.amazon.com/dp/B01N6EKHZR

For the multimeter, I have this one and it works perfectly fine. That module you linked won't work, though. That mudole's module's minimum input is 4V, and the Pocket runs on 3V with fresh batteries. Something more like this module would work. I could be wrong though, as I've never done this mod; I just shoved a lithium-ion battery into my Pocket and it works great.

Also, going down the rabbit hole is really fun! I started with the backoight backlight mod, then I did a prosound, then a USB rechargeable battery, then a bass boost, then an amplifier, and I'm debating doing a bivert, though with how little space is left after the preceding mess, I probably can't. :P

EDIT: Wow I butchered the spelling of "module"

EDIT2: And the spelling of "backlight"

What do you mean they don't like the small increase? you're looking for DC to DC step up modules like these, just check on the current capacity.

https://www.amazon.com/Mini-DC-Voltage-Regulator-5V/dp/B01N6EKHZR/ref=sr_1_7?ie=UTF8&qid=1549996952&sr=8-7&keywords=3.3v+to+5v+step+up

​

Is there a reason why you don't want to just get a normal USB battery? They're just 18650s with the necessary charge and boost circuits built in already