I accidentally stumbled in this outfit this morning in my quest for Sounds. Though for Boats they may have a place in our Trains as well. The Whistle on the Steam Boats one is the best I have heard other than a DCC Chip and the Diesels are nice and clonky. A little on the large side but may fit ok in a Diesel or Tender. 3 Sounds can be activated by RC so may work ok with the varying Battery systems out in the Parish. Listen to the examples and see what you think.
https://www.harbormodels.com/sounds.html
https://www.harbormodels.com/sounds.html