I made this for "BESTTEN 12-Outlet Heavy Duty Workshop Metal Power Strip" ordered from Amazon. (https://www.amazon.com/BESTTEN-12-Outlet-Wide-Spaced-Protector-Extension/dp/B01CCX0LJ2)
Designed in Fusion 360.
The tray is the only accessory I've designed so far, but more are planned.
The design is for this specific power strip, which is 38mm height x 32mm depth. Similar power strips may also fit. Original design files included if you need to adjust things.
Print everything sideways -- see pic!