does anyone know where you can get input gears for these transfer cases?

 

You might try http://quad4x4.com/.

 

Ebay is source. 4by4 shops have access to parts.

 

I contacted a fellow on E-bay. I just called him this evening and he seems quite knowledgable about these trans/transfers.
I contacted him about an NV4500 for my tranny conversion that he had listed on E-bay.
His E-bay user name is jrjeepparts.
He is in IL. I won't put up his phone number but if you want to talk to him you can go look him up on E-bay and contact him through his profile info.
His Name is Jim.
His prices are good as well.