Theres a mu.run on (at least) one of the disks archived at the Computer History Musuem, listed at

http://xeroxalto.computerhistory.org/_cd8_/alto/.index.html

http://xeroxalto.computerhistory.org/_cd8_/alto/.mu.run!2.ht...

but I don't know if there's any way to transfer it from a disk image to an actual Alto disk?