Thanks for the suggestions.
Maybe just a dual outlet extension cord
I really like the dual outlet extension cord, so I will see if I can find one locally.
I needed 3 outlets so used about the smallest power strip I could find
I think a power strip with just 2 ports will fit, but the only one I found costs 18,-, compared to just 4,- for a 3 port one.
Or just buy a terminal block for a few pennies and wire your mains supply into one side, and all you devices into the other.
I still have some scrap pieces of wood/plexi left over, so I could make a small cover myself. I am correct that I could then wire it like in the picture? Any preference for one way or the other?