This place sometimes has a selection of Rosewood, Ebony, etc picks-
I got a couple packs, but don't use picks much, altho when I tried the ones that they sent,
they were all good and consistent quality and the different types of wood had very noticeable difference to attack and tone.
Only thing I didn't like was that the thumb and finger contours left more of the tip sticking out that I prefer- the point could be rounded off a bit, tho and they'd be great.
And, altho it seems they're made for guitar, they're thick enough for bass.