I have one shown on AMazon as a disabled assistance. Cost now not much under fifty quid. I purchased mine about 15 years ago for under a tenner. It is very good for pushing those windows open and closing them BUT it does not push the lever to unlock them. I used it for the small top windows at my house for many years, but had to climb up each Spring to push the button to 'unlock' them. After that I never fully closed them all summer so I could use this poll.
Never found one which could also push that button.
Easier to use on the large windows in my flat, when closed I can easily reach all the handles, so no problem with pushing in that locking button. When I open the windows (as I often do), beyond the safety catch, I use this long handled thingie to reach out to pull them back.