For sale on ebay is my custom shift knob. starting price is $6.

WRX shift knob | eBay
For sale is my Subaru WRX shifter knob. I had it on a 2015 WRX. Can’t say for sure, but it should fit all the WRXs since 15. Also don’t know about the STIs. It is made of Osage Orange (sage) wood with a steel nut inside.
www.ebay.com