Donations are contributions as well. However once free and open source projects does not have employees, what you want may or may not be done. It all depends on how important contributors think this issue is
What you can do is to hire a freelancer to program it for you, so surely you get what you want
'surely you get ...' ---- not necessarily; contributions that satisfy feature requests are unlikely to be welcomed with open arms if they don't already fit the core maintainers' overall strategy. Some projects are very flexible about this; but Gnome is notoriously not.
... and even if the commissioned feature patch remains private, it might break on the next update, which would be a waste.