Depending on your definition of
"portable"... an HP-150 with the built in
printer
could do lower case (I'm pretty sure).
An HP71B + Datacomms ROM + 2225B Thinkjet printer + either an HP82164
RS232 interface or HP82168 modem is portable. It can certainly do lower case.
Although personally, I'd rather carry a VT220....
Other 'sillies' would be just about any laptop computer + a portable
printer. Or the Epson HX20 + suitable software (the printer on that
machine will print in lower case). I assume the printer cartridge for the
PX4 can too.
-tony