General Tools & Instruments 370 2 Power Alnico Magnets
Alnico magnets are strong and permanent.  They are made of aluminum nickel and cobalt and work under normal conditions and temperatures.  They come with removable keepers.  This power alnico type magnet is a horseshoe type and is 2 oz size, and has a 13 lb pull.  It is 1-1/8" wide with center hole for attachment.