Soldering Iron Holder With Magnetic Base Stand
This should fit most of the cheap soldering irons you find on eBay.
When printing the base you can pause printing @ around 7.3 MM to drop in a 1/2" x 1/4" round Neo Magnet or you can just use some double-sided foam tape on the bottom of the base to secure it.
You will need to super glue the base to the holder.