My question would be Jet by Sublogic, and ... most unfortunately Xenix x86. Which leads me to believe that... you need a very low power cMos CPU, to have that battery life.
There are 12Mhz Harris cMos 286s but they are collector items, and the next step is 486slcs, which may run Xenix 386 w/ TCP/IP stack, rather well.
https://www2.eecs.berkeley.edu/Pubs/TechRpts/1994/ERL-94-65....