Install a Ceiling Fan Retrofit Junction Box (Support a Heavy Light Fixture) - YouTube
Ceiling fan mount install : r/AskElectricians
Old electric box won't fit new ceiling fan mounting bracket. - DoItYourself.com Community Forums
How to Install a Ceiling Fan Brace - YouTube
Ceiling Light Fixture Mounting Bracket [Upgraded Version], Ceiling Fan Mounting Bracket, Universal Light Fixture Parts with Screws, Swivel Junction Box Adapter, Light Fixture Crossbar for Light, Fan - Amazon.com
Commercial Electric 4 in. White Mounting Plate and Mounting Screws for Commercial Electric LED Strip Lights Covers Standard Junction Box 54657101 - The Home Depot