[Harp-L] harmonica key for a minor key

[Hugo Scott]

Hi there,
I had a look through the archives but I couldn't see the answer to my
question: Someone has asked me to play some harmonica in a tune in F minor
but as I only have diatonics in the most common keys I was wondering which
key would sound good with Fm if I was playing a cross-harp style? would it
be a B flat ? Or maybe a D flat ??
Thanks for any suggestions !
Hugo Scott