Here are frames and bottom plates for Paper Bits, all kind of Paper PCBs and some other boards.
All plates and frames were made with openSCAD.
Frame for the Raspberry Pi HQ Camera
Frames for Paper Bits
Frames for Paper PCB
Bottom Plate for Arduino
Bottom Plate for Raspberry Pi
Bottom Plate for FPGA Boards

These 3D objects are designed by Wolfgang Spahn 2016-20.
They are licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.