Where can I purchase just (1) ceiling fan 3 speed pull chain speed switch ( K.T.E. 308-A) ?
The4 fan was made by Hunter.

There's 2 links on this post:
https://www.askmehelpdesk.com/electrical-lighting/kte-308-3-speed-pull-chain-switch-200788.html
I couldn't find your switch, maybe they can.

Home Depot,Lowe's,Ace Hardware Etc

If the fan was made by Hunter, get the part from them.

Call Hunter Fan - Ceiling Fans, Air Purifiers, Humidifiers, Thermostats (http://www.hunterfan.com)