I found this on Amazon. Little expensive but if your looking for a set of buttons you can mount within reach of your thumb this might work for you also. I used 3M double sided tape. On the C109 it’s a flat surface under the horn switch. The 3M tape holds it as well as a screw believe it or not. I don’t have to baby it while pressing a button. I did however use a little piece of fishing line as a tether just Incase, but I’ve found it’s not necessary.
I have the Tsukyu fearing with the stereo. The radio controls that came with it suck.
Rockford Fosgate PMX-BTUR Universal Bluetooth Steering Wheel Remote Controller for Car, Truck, Boat, Motorcycle or UTV https://www.amazon.com/dp/B07M59WDF6..._PcDyFb25Z95Q4