These common yellow stir-plates by Thermo Scientific/Cimarec have plastic potentiometer shafts, knobs easily broken off.
But Thermo no longer sells the replacement pot assembly! The pots themselves aren't sold anywhere either. It's an OEM part from CTS Electrocomponents, with a big plastic spacer and extra-long shaft. And power switch.
BUT, we can dissect the broken pot and reconstruct it. Keep the shell, but use internal parts from other pots.
Buy these 100K pots:
450D104-8-ND (digikey) 450T328F104A1C1 (digikey)The long plastic shaft from the 450D104 can be cut down and used to replace the (too short) metal one. And, the rotor-assembly from the metal one will work inside the original Thermo pot.
Here at Chem Dept. the undergrads occasionally shear off the pot-knobs. Should we just throw away a perfectly good $500 stirplate?!! We can fix this.
Other repair parts are still available, see