I think punching the holes would not be a big problem to overcome. .... arrangements for 20 notes,
I have notes on punching Smith Busker rolls at
http://www.wallace-venable.name/mechanical-music/
On a sub-page you will find several 20 note arrangements.
.... getting rights to the copyright, ...
Assuming you are in the USA, there is no reason to expect trouble for PLAYING any music on a crank organ.
Tunes from before 1928 are essentially ALL free of copyright protection.
Most other music copyrights in the USA are managed by actions of ASCAP, the American Society of Composers, Arrangers & Publishers. You can read their rules on their website, but it seems clear to me that the basic rule is:
ASCAP does not seek payment from musicians.
For public performance, it is the venue which "must" pay for a license. If you play in a street, school or park, you are covered by the same annual license which the owners obtained to cover parades by the high school band, student rock groups, etc. (Your community does have a license for this, I hope. They are required to do so.) Same rules apply to bars, etc. as long as events don't gross $25,000 or so.
You may NOT publish sheet music, sell recordings (including rolls and CDs) etc. without obtaining expensive rights.