I am in Australia.. and looking for a standard Verizon USB 4G modem it seems they charge ridiculous prices for them. It might be worthwhile hunting one down second hand and getting a new data sim for it.. if you cannot just buy more data.
Lots of LTE routers work with USB modems rather than inbuilt but you do need to google hard.
The other option is to use a phone.. not new but a second hand cheap Android type phone if you cannot locate a USB modem.. again some routers are designed to handshake with a tethered phone for internet.. check internet carefully for exact model of phone supported. Mostly it will be standard Android for obvious reasons.
Asus routers I use lots.. this is supported. See
https://netosec.com/tethering-mobile-phone-to-home-network/
I presume where you live you don't have coverage from other 4G suppliers.. or wifimax etc.. there are often other internet services available.. even satellite which will become more common with stuff spaceX is doing. So future is looking bright for people outside of main cities.