Have you contacted Kala? They sell cases and may have something for their longer instruments.
I don't think O'ahu makes an extended case, but it might be worth a call to TUS to see if they make one, or have an idea of where you can look for one.
Mim sells a case for 8-string and longneck tenors, but it's only 31". If you added bolsters, maybe a hardcase for a longneck baritone or a small parlor guitar?
As an option, Jerryc41 has posted a few times about making custom cases for a few of his instruments. Check them out.
Also, Google "making your own guitar case". I'm sure you'll find videos on that.
Good luck.