I’m looking for a plugin that can mass-change users’ passwords automatically on a monthly basis to what I choose

I’m looking for a plugin that can change users’ passwords on a monthly basis to what I choose (not reset). To clarify, I change my 50 users’ passwords on the first of every month to something similar to this: December287491, with every user having a different number. I then send them their PW for the month. I have been doing this manually but would love a plugin that can change their passwords for me.
Or, is there a way to access the password data and just update it all at once?