What is your "holy grail song" that you cannot find?

I'm looking for a cover version of "Chest Fever," which was written by and originally performed by The Band. Currently, the best known cover versions of that song were done by Three Dog Night and Widespread Panic. 

Mademoiselle Nobs can only be found on Pink Floyd bootleg "Live In Pompeii". That is THE MOST psychedelic song ever been recorded. 

That's where Richard Wright's dog (Mademoiselle Nobs) was singing on stage.

I can't even find information that they covered it.

@thecarpathian I heard it a couple of times on WKLS (96 Rock) in Atlanta back in the 70's. I didn't hear it again until around 15 years ago, when I heard it on KGSR in Austin. So, I'm beginning to think that it was some kind of limited promotional item that only 1970's DJ's would know about. That theory could explain why there is no info on it and why it is so hard to find  

Hot Smoke and Sassafras, by the Bubble Puppy.

I heard that song in the early 60's and totally flipped out over it. Can't find an LP or 45.