"Sleeping Bag" is actually on the ninth ZZ Top album, Afterburner.
Excuse the nerdiness, but as you might've guessed from my username, ZZ Top is my favorite American rock band. I don't think they get credit for just how tasteful and quirky and funny their stuff is, even before they got to Eliminator and all of the (great) videos that we've all seen a million times.
Their discography hit a bit of a rough patch after Eliminator, but their 12th album, Rhythmeen, is one of their very best. I highly recommend it, and I'm sure you can find it in the cheap bin of any used record store you care to visit.