I just transposed a song with the note sequence: B-B-B-D B-B-B-D#
No whistle I have seems to do a good half-holed D#. Either the note is too weak (and easily overblown) or I just get hiss. Not to mention: half-holing a D# requires all manner of contortionist finger dexterity.
Is there a crossfinger alternative?
You need a whistle with larger fingerholes which makes for easier cross fingering.
I can’t think of a cross fingering, but you can half hole in several ways: shade either the top or the side of the bottom hole, tip your finger up to expose part of the hole vs bending your finger to do it. Experiment.
Was it a piping tune?? Uilleann pipes use this note quite a bit to great effect, but they also have a dedicated hole for it. I don’t imagine it would be hard to add one to a whistle either. I can’t think of any other way to get the same timbre or quality of sound that you’d hear in a piping tune anyway. Best-
Bri~
Sounds like a Mack project to me, Bri…
Speaking of which, are we doing any CO/WY road trips this month? PM me… (can’t email at work) 
Could you give the full score? This seems to be playable easier on a A, maybe G, whistle.
Would work only if it doesn’t go way beyond an octave range.