The album "Nightbirds" by Labelle with the song Lady Marmalade is not available for streaming or purchase. I managed to find a used CD on Ebay for a reasonable price but it's pretty rare.
What is your "holy grail song" that you cannot find?
For me, that song is a live version of "Chest Fever" by Humble Pie. My guess is that it's a vinyl bootleg that is virtually impossible to find. So, if anyone knows anything about this recording, please provide some details. In the meantime, maybe one of us knows something about a rare song and/or recording that some of you are looking for.