Some euphonium concertos with orchestra accompaniment include the Cosma, the Linkola, the Feinstein, the Horovitz and the Jansa Concerto Iberico. There are others but I can't remember them at the moment.
Plenty of trombone concertos also come with it, the David, the Bourgeois, the Rimsky-Korsakov, etc. Also worth considering is the Mozart K191 Bassoon Concerto, I know many euph players have had success with that.
University of Miami - BM Euphonium Performance '21
Indiana University - MM Bass Trombone and Euphonium Performance '24
Besson Prestige 2052S
Courtois 551BHRA
Conn 88HCLSGX
Various Greg Black mouthpieces