Try a $20 upper back brace. Wear it for 20 minutes at a time while you're working. It conditions your upper back to straighten up and become less rounded.
https://www.amazon.com/Posture-Corrector-Men-Women-Truweo/dp...
https://www.amazon.com/Posture-Corrector-Men-Women-Truweo/dp...
Also...I'm skeptical about these as I've heard they train your muscles to be lazy – the brace does lots of the work, so when you take it off old habits kick in because you're muscles can't do the same job the brace was doing.
But I guess the limit of 20–60 mins a day is to prevent that?
Have you tried it yourself? Not doubting, just always have some skepticism of reviews on Amazon haha
You also need to do strength training.