Mark, my tech never replied to my inquiry about a sound file for your engine. My suggestion now is - if you don't care about the prototypical whistle - just choose a whistle you like. Any sound file can be loaded on your engine, even a diesel horn!
I had my K-Line B&A 4-6-6T converted to PS3, but MTH doesn't have a specific sound file for it. A chose a NYC Hudson file, because both engines were built by Alco and it sounds great. Another MTH engine with a whistle I really like is my Russian Decapod.
There are lots of possibilities! Let me know how you make out.
John