lighting - My circular old work electrical box is too small for the light fixture mounting bracket - Home Improvement Stack Exchange
Mounting Light Fixtures - Fine Homebuilding
Southwire Smart Box Adjustable Depth 75 lbs. Light Fixture Support/50 lbs. Ceiling Fan Support MSBFAN - The Home Depot
Commercial Electric 4 in. Round 16 cu. in. Non-Metallic Ceiling Fan/Light Fixture Saddle Mount Box for New Work CPB16NM - The Home Depot
electrical - Trim piece to allow flush install of exterior light with surface mount box - Home Improvement Stack Exchange
Commercial Electric 5 in. Mini Closet Light LED Flush Mount with White and Bronze Trims Fits 3.5 in. 4 in. Junction Boxes 7-Watts 650 Lumens 564361410 - The Home Depot
11 Types of Electrical Boxes and How to Choose One
Commercial Electric 4 in. White Mounting Plate and Mounting Screws for Commercial Electric LED Strip Lights Covers Standard Junction Box 54657101 - The Home Depot
Siding Mounting Block, Built-in Box For Light Fixtures — Primus Cable