Magnetic Olympic Weight Holder

You need this magnetic hook from Harbor Freight, although if you have other magnetic hooks with a screw then you might be able to make it work. 
 

U.S. GENERAL 25 lb. Magnetic Hook

https://www.harborfreight.com/hardware/hooks-clips/magnetic/25-lb-magnetic-hook-black-58106.html
 

Super easy to install. Just unscrew the bolt holding the hook in, remove everything including the washers, and screw the printed part in place with the bolt and nothing else. 
 

Added step files so you can lengthen it if needed.