> Problem is the CE device doesn't have an Intel x86 processor.

The good old HP200LX palmtop is a 80186 based 640k DOS compatible, and
I have already used the DOS version of MPASM on it.

It has an RS232C port, too, and DOS command line programmers (with
external power supply or battery) can be used with the HP200LX.

The HP200LX is old but still my favourite palm size computer!

You can get one cheap on the used market (it's out of production I
believe).