The Inseego models m2000/2100 are probably cheapest entry, but are usually locked down on interface configurations (to prevent rooting/uncapping) although there is at least one or two vendors that can program them however you want for $50-100 on top of the about $1-200 USD for the device. There are a few netgear options that offer more flexibility for routing options but the portable ones start at a few hundred, and their more permanent setups are in the four figure range. While not what you asked for, my personal suggestion would be getting a router that supports openwrt and has usb and hooking up to cheapest 5G handset you can buy. Flash openwrt on the router and add the tethering packages (I believe may be default now and/or you can customize build online to add necessary packages for iOS it is I believe libimobiledevice). This also has the added benefit of being able to upgrade just the router or just the phone/radios i.e. to support wifi 7, or whatever new frequency bands get implemented.