If you have Amazon Prime, that documentary (Unsung Treasure) is included-and it is great. Rekindled my appreciation for David Bromberg.
BTW his latest (to me, at least) album "Only Slightly Mad" is really great. After hearing such heavy hitters from the same era like Bob Dylan and Neil Young turn recently turn out album after album that are, at best, one listen affairs, it really is heartening to have an old master come up with some of his best work now.