Keep in mind when powering both RaspberryPi from the same powerbrick: some chargers briefly turn the power off and restart the charging when connecting or disconnecting another device. Some do this only between the same type of ports but frequently restarting your RaspberryPi is probably not what you want.

I printed a few of these: https://www.thingiverse.com/thing:4820432 And bought a few of these: https://a.aliexpress.com/_ExBOJ6F Then store everything in vacuum bags after print. Works great for me!