This is a improved version of my previous design.
I remove the key holder parts and hold the keys directly by the cover plate. This makes the whole things thinner and smaller. Also, only 2 M2.6x6 screws is needed and washer is added to adjust for different key thickness.
This design can hold 4 keys. you may adjust the pole to put more keys in it.
To maintenance the strength of the cover piece, it is recommended to print them in 100% fill