Hi patb,
If you're talking about the movie "Nothing but the Blues", which has Eric Clapton covering songs from most of the Blues "greats" and as much as possible even changing the model of guitar they used to sound as authentic as possible (and which was produced by Martin Scorecese), you're unlikely to find it at any regular movie/DVD store, since Clapton, for reasons unknown, decided after it was done to NOT let Scorecese release the film - even though almost everyone I know who's into the Blues, thinks it's one of the best Blues movies they've ever seen and EC is playing at his A++ (very best).
I have a copy, which I got about 8 years ago, but it involved following threads online until I got to the source of the person who currently had a copy of the movie - which was made from the ONE TIME PBS broadcast in Europe and was luckily recorded in full by someone and then an underground ring developed by which you could put your name on a list, and the ONE copy of the recording of the movie that this group had was sent to the next person on the list, who then sent it onto the next person from them on the list, and it involved a lot of honesty because one person deciding to just keep the "original" copy of the tape would have pretty much put the spread of this precious music at a standstill (or someone would have had to restart the whole thing with their "copy of a copy", which, even though it was on a DVD, might not have had the quality of the original DVD copy that was making the rounds.
I had to wait for someone in England to send me his "original" after making a copy of it, and then I had to mail it off to the next person on the list after me, which was someone in South America (so the postage wasn't cheap getting it to the next stop), but it's really a PRICELESS movie and no one I know has any idea why Clapton didn't want the movie released. But, I do have a digital copy of it, so I could upload it to an FTP server I have (that goes along with my domain jamessignorile.com and I'm willing to put it up and share the URL (a Dropbox URL) to make it available to everyone on this forum, OR, if Griff would allow me to upload it to this site, I could also do that and I think it would be more accessible if done with a copy on this domain.
If someone could ask Griff if he'd allow me to upload a "zipped" copy of the digital copy of the DVD to this site (I would but I'm up to my head with other stuff to do (I started a Blues band and a leader of it, I have SO much work to do getting music ready and scheduling rehearsals and answering the never-ending flow of questions I get everyday, as well as weekly rehearsals and gigs (we've only played out 3 times so far, and getting all the equipment and logistics involved with running a band (and a large one - as many as 12 people are band members and synchronizing them as well as helping to run the local Open Mic here in town (which has had at least 100 people both performing or there as audience members, with more expected once the winter holidays are over) is a humongous task).
Let me know if you're interested in my uploading a copy of it - and also if someone can ask Griff if he'll let me post it on this site, then I'll do that and leave it available for any forum members who would like a copy of it.
Jim