Since light and portable seem to be of importance to you, I will make a different recommendation and it's reality based as we use it ourselves as a monitor.
We use a Roland Mobile Cube as a monitor. Very small - runs on batteries or AC power. Plenty of volume for solo or duo. It is also capable of playing small gigs or busking.
We run a line out from our Street Cube EX to the Mic input on the Mobile Cube. Works great. You could just use the cable suggested by Yamahaguy in the same way.
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Roy
Ibanez, Recording King, Gretsch, Martin
G&L, Squier, Orange (x 2),
Bugera, JBL, Soundcraft
Our duo website -
UPDATED 7/26/19