I can't find it anywhere, but it's played 3 separate times...
- 20:48 season 1 episode 26 "then x and x after"
- 16:44 season 2 episode 11 "ging x and x gon"
- 18:47 season 3 episode 10 "very x sharp x eye"
The soundtrack isn't included in the original soundtrack CD, so it is unreleased, you can't search it by soundtrack name. This list shows you soundtracks included in every episodes. See ep. 37 because ep. 26 doesn't have a list (cuz it's a filler, doesn't include in either Blu-ray or DVD).
I don't have names but, the other guy covered it pretty much. These playlists would be to your liking most likely: https://www.youtube.com/playlist?list=PL7636F65EA6C7228C, https://www.youtube.com/watch?v=wFeYG_GYxoQ&list=PL24ACDF1A713BEE0B
The ones that closely matched to the ones in query were:
The song is "JUST AWAKE" from "FEAR, and Loathing in Las Vegas". Here a YouTube link.