Welcome to the forum @Olyjia
Have you tried using the beta search on the App ? You can search for “sits with pianos”
I tried it and 20 or so sits came up that had pianos (but none were for long sits) . You could favourite them and you’ll be notified when they next list dates ( which maybe for longer duration next time around )
https://forum.trustedhousesitters.com/t/introducing-search-plus-beta