I have very similar 2.1 speaker system but I picked up a separate USB volume dial:

https://www.amazon.com/dp/B016U2KXCG/ref=cm_sw_r_cp_apa_i_B5dlFbXGXNCDQ

I have it mounted to the top of my cab out of view with a 3M velcro strip (don't recall if I had to also pick up an USB extension cable as well). Works out of the box, no software needed. Pressing the dial will mute the volume.

With this set up, I'm never using the proprietary volume controls on the speaker system so I don't have to worry about wear and tear.