This has been done to a point in Mexico, with the Audofefensas. They were absorbed into law enforcement after a while, and given uniforms and guns. The situation came from the cartels, but that is a place to look. Also, many in minority communities have spoken of organizing self defense teams since the 60s. Not just the Black Panthers.

https://stmuhistorymedia.org/autodefensas-mexicos-self-defense-forces/

And of course, a take on this from the far right

https://thefederalist.com/2020/06/09/if-you-want-to-know-what-disbanding-the-police-looks-like-look-at-mexico/