Erccre147 is a talented guy who arranges pony music for the trombone, baritone, and tuba. His most recent piece of work is for Find A Pet, and Erccre147 has done a beautiful job as always.
The music for trombone and baritone can be found over here, and the tuba sheet music is here. Thanks for sharing, Erccre147!
If you want to see more pony music from Erccre147, simply look for his name in the big list of songs for season one or season two.