[nehal3m]

I'd be the first to admit this alternative is less than ideal since it adds yet another device, but you could carry a battery powered MiFi router (even power it off to conserve it) to supply a mobile connection, and then a feature phone for calls. Plus of course whatever you'd want to use to go online.

I used a TP-Link M7650 when I was cut off from fiber for a while and it worked great for me.

[dredmorbius]

You certainly could. There are also pluggable modems which are powered directly off, say, your laptop or tablet.

There are also many dumbphones which act as hotspots. Most carriers have low nominal charge for ~100 GB of 150--300 Mbps connectivity monthly.