So you have to buy the switch assembly
and then pair it with either part
(link to second one: https://www.ktm.com/en/powerparts/so...trol-587cce82/
prices are woolly but as far as i can find you can expect to pay us$360 for the cruise control and another us$150 for the switch.
Why it wouldn't be done in software using the navi buttons i don't know.
I don't do a lot of long rides and over us$700 for a feature plus the labor of fitting it AND having to take it to a dealer to get it activated (assumming it works on the duke 790) is not worth IMHO.
Lets not forget, adaptive cruise control with a freaking lasoooor on your lexus when it came out in 2014 was only $500 extra.