Sounds like you need higher amperage for the project. How about connecting the Pi to a USB charger and hang that off something like a portable PowerStation?

USB Charger - https://www.amazon.com/Charger-Charging-Desktop-Multiple-Compatible/dp/B09JWNQYZF/ref=sr_1_6?keywords=usb+charger&qid=1647890179&sprefix=USB%2Caps%2C114&sr=8-6

Power station - https://www.amazon.com/Jackery-Portable-Explorer-Generator-Optional/dp/B082TMBYR6/ref=sr_1_3?crid=A00QY585UHDV&keywords=black+and+decker+power+station&qid=1647890310&sprefix=black+and+decker+power%2Caps%2C142&sr=8-3

If a truly large run time is needed, a larger unit like the ones Jackery makes for campers is a good choice

Although an expensive one...

Jackery Explorer 300 = $1.02 per watthour

Jackery Explorer 1000 = $1.097 per watthour

Chinns LiFePO4 with ChargeIt! USB-C PD supply and $120 AC charger = $0.36 per watthour.

If you want a solar controller also, add $22.. brings it to $0.384 per watthour.

Add a 1000 watt inverter and you are still under 50 cents per watthour - half the price of a similar Jackery.

Sure if you want an off-the-shelf, ready-to-go unit and have the money, Jackery is OK. Buy the parts separate and you can save a good bit of money.