Some old TV's that do not have composite but do have rf input can be used with a vcr
My favorite is to use an old dvdrom player with composite and audio input. You can always attach a Raspberry Pi to the back of the unit to make it super portable.
Even an old portable tv with composite input can be a choice! In the case though it is only black and white.
Then again you can use your tablet via xrdp to act as a screen for your raspberry Pi.
Last but not least is the old Trs-80 monitor. No sound and is only black and white. You also have to provide a +5 volts line externally..
There is always those inexpensive mini portable monitors, but they may require 12 volts to work. Normally used for automobiles.
Note: for the Raspberry Pi Zero will require adding solder points for the composite output and an audio filter. The specs for this are in an earlier article.