Colombia's National Administrative Department of Statistics hosts shapefiles that have official municipality boundaries here: [https://geoportal.dane.gov.co/?descarga-marco-geoestadistico-nacional][1]

Also, as of today, GADM is still missing municipalities in Amazonas, and in the OpenStreetMap data, some municipal boundaries intersect their neighbors.

Edit: Possibly this link is nicer (the CSS on the first link isn't great for some browsers/viewport sizes): [https://geoportal.dane.gov.co/metadatos/descarga_mgn/][2]


  [1]: https://geoportal.dane.gov.co/?descarga-marco-geoestadistico-nacional
  [2]: https://geoportal.dane.gov.co/metadatos/descarga_mgn/