Have you looked at Rhodium's page yet? Magnetic stirrers are basically composed of a case, a magnet and motor to spin the magnet, stirbars are magnets sealed in plastic or glass :) The link is :
https://www.thevespiary.org/rhodium/Rhodium/chemistry/equipment/magstirrer.html (https://www.thevespiary.org/rhodium/Rhodium/chemistry/equipment/magstirrer.html)
It's a lot easier to buy one than make one ;D ;D