Will turn on but I have to choke it to turn off

Stihl only wants dealers to fix their stuff. Either the switch is bad or what it connects to is bad. Most ignitions ground the ignition system to turn the engine off.

You can't buy Stihl parts online either.

Check the area around the switch, you may have to take a shroud off to see/get at it... Sometimes an accumulation of wood dust, and oil builds up around the switch that won't allow the grounding that K.I.S.S. mentioned.