I simply back my normal sizing dies out a turn or 2. Seems to work well for my most of my rifles. 
I bought a neck sizing die from CH4D about 2 years ago for a 40-70cal sharps bottle neck which actually works well for most other case types that are similar in overall case size. I see that CH4D does show that neck sizing dies are available on their website for $104. Have you talked directly with CH4D. (You need to Login or Register to view media files and links)