Is there any pentatonic that you can use under a locrian mode fine? like the same way you can use C minor pentatonic under C dorian, C phyrigian and C aeolian?
Yes. You can play a minor pentatonic off each minor degree of the major scale.

So if Bm7b5 is being played, you can create the sound of Locrian by playing D, E or A minor pentatonic, because those are the minor degrees of, in this case the C major scale.
Quote by Punkismygod
you really are a theory genious, thank you!

No problem Spider Man

I just wrote out the notes of each of those pentatonic scales.

Dm Pentatonic is best as it contains:

D (b3)
F (b5)
G (b6)
A (b7)
C (b2)

But do experiment with all three to see what sounds good.