Thanks all...
Good ideas, I had thought about using the seat tube bottle holder holes with a curved piece to match the tube curve, but did not think about using the front down tube as well. I don't KNOW if it is brazed on or welded on, that's my problem. I'll take it to someone knowledgeable and see if they can do the job. If not, I'll look into the adapter method. My last resort will be an E-type derailleur or a custom made "arrowhead shaped" tube clamp and a bolt on derailleur.