I made a small attachment for the PcEngine to connect a small LCD screen and sound out through a small amp and two little speakers.

Here's the aliexpress parts I used for the Lcd and audio amp https://www.aliexpress.com/item/1005006825697479.html
and https://www.aliexpress.com/item/32950317822.html

I then use the pc engine rgb booster thing that attaches to the back of the console & use the composite out to the screen and the audio out to the audio amp:
https://www.aliexpress.com/item/4001181092119.html

For the speakers I used small speakers I had lying around . you'll find those easy enough on ebay or salvage em from toys .

For power I use a 12v supply and splice it to power both the screen and audio amp

Here's a video showing the entire process : https://www.youtube.com/watch?v=wE0tOXA0oQU