I have looked and looked and have found absolutely nothing on Geronimo Jackson. I know that they are fabricated for the LOST storyline. But I noticed something weird on their lostpedia page. I looked at the picture of their album cover and the man at the top holding the guitar looks a lot like Mr. Friendly or Tom from the others.
The producers have stated that the band members have "kind of gone missing" since 1971. Do you suppose the band went to the island in the seventies and that man truly is Tom.
Far-fetched but, why not.