As you already probably know, getting an original neck is a daunting task.  And most 3rd party necks are very expensive.  I read in another blog that Phil Barone sold a neck to someone with the same horn as you who was also missing a neck, and the owner was very happy with that neck. I do no know if he still makes those particular necks, but you can try contacting him at his website to find out:  
https://www.philbarone.com

Good luck with your search.