Well, for v0.230 these files are in the 'Source' download (file 'messui230s.7z') on this website:
(Of course for 0.234 it should be 'messui234s.7z', but it's not availbale yet)
For MessUI32 v0.230 I first used Robert's main file (messui-master), then copied this small source update (messui230s.7z)
from ProgrettoSnaps over it, and finally I made these 2 changes mentioned above (at least since MessUI32 v0.230
that doesn't run anymore without these changes).
Edit: I just saw, that these 2 files even exist in the original 'messui-master' in the folders 'src\mame\' resp. in