I have something similar, i used drawer slides and made a flat platform the slides out from under my desk, and then attached a short pipe to the bottom, i then used a similar monitor mount like the one u linked but slightly different i will link below. I then made mounting platforms that i then screwed the hotas into.
https://www.amazon.com/gp/product/B00PZDB2HM/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1
I just set my Hotas 4 on a computer chair with 2 of these:
And then I used heavy duty Velcro to attach each side of the Hotas to the mounts. The wire between the two halves is long enough for this set up. I'm loving it!
Edit: your chair has to have arms for these to clamp to.