I have a couple spares in the console (repaired broken knobs). I did the same repair to the last couple new ones before I instaled them, one lasted a twice as long as normal and the other is still working.
I wrap a piece of safety wire around the area where it breaks and then coat the area with steel filled epoxy (JB Weld) to encapsulate the wire and coat the plastic shaft. Don't get it too big or it might not fit into the hole around the shaft in the dash (I check them and file them down before they go into the console).
Hope this helps.