Then you have a string of devices that need to be connected together in a more n rigid fashion, either in separate compartments of a bag or case with a USB cable between, or strapped together with tape.
"PiJuice will use up to just five of your GPIO pins (just power and I2C), the rest are free to diversify your project. The stacking header allows you to continue to use your existing HATs and add-ons with PiJuice." from https://uk.pi-supply.com/products/pijuice-standard
But sure, some people/projects might prefer to shift the hardware to not be attached to the Pi. I wouldn't be surprised if you could find a product that does that too, or at worst I presume a basic plastic box (there's probably pre-made ones for the size of various Pi HATs? and of course 3D printing) and some fairly simple DYI wiring to connect the 5 pins through a cable wouldn't be too tricky.
I used one of these for about a year on my PiHole, but switched to a standard UPS because the hat's LiPo started bulging from all the heat generated by the Pi's processor.
The hat is a great idea in principle, but because the battery is sitting right on top of the processor, it doesn't stand a chance given that lithium batteries are fairly temperature sensitive.
Hit Amazon.com and search for "raspberry pi UPS" and you'll find plenty of options. Or more generically try search terms like "mini ups" or "router ups" or "dc ups" - loads of options at places like Aliexpress as well.
Here in South Africa with rolling blackouts happening fairly regularly these days a lot of homes have something similar to keep internet connectivity live when it happens, with a lot of those options having USB outputs as well.
Mine came from https://www.geewiz.co.za/ups/124927-acconet-poe-48v-24v-smar... Looks like this may be a South African domestic brand though (and you probably don't want to order from a South African site unless you're living in the country to be honest).
One thing to be wary about though is max power if you're trying to run a raspberry pi with hard drive attached off one of these devices. A lot of these devices cap output on the USB ports at ~5V/2A (which I think was the USB2 max whereas USB3 allows for more). If you're running off an SD-card or SSD you should be fine, but 2A isn't enough to start a pi from an attached 2.5" HDD in my experience.
Not usb but mini UPS to keep your modem going is a common thing in India nowadays given constant power interruptions.
Ironically I got mine before I learned of the power cuts in my new home while building it. I was just merely thinking of edge cases of how a smart thief could undo my security cameras and figured cutting off the power would be one option I need to prepare, so got this UPS to backup both the modems (and redundant internet connections) and the home bridge for the battery backup security cam.
Not quite that but I ordered an Eaton 3S 850, which is a beefy power strip with built-in battery and looks like a decent compromise for cases where you don't really need a huge noisy rack-mounted UPS, but something that can do a bit more than just a Raspberry Pi (i.e. several Pis plus the router).
But would you only need 5V? DSLAMs here have an hour or so of UPS capacity as well, so if the router stays up, so does the internet connection, same with 4G/5G routers. Though I guess a 5/12/24V DC mini-UPS would still be a lot easier than actual 110/220V AC.
