I find it interesting Graf is selling this brass. You might contact them and see if they might be able help. Why are they supplying this brass? Some background on that might point you to some dies.
I also would go back to CH4D. Since the owner Dave Davison passed away the company has been reorganized and is now back to being CH Tool and Die-still operated by the Davison Family.
Here is a link to their die page and the part on custom dies.
https://chtoolanddie.com/calibers/groups
I find CH's price and wait time reasonable.
I could have went the CH route for my .404 Exp dies. I had the gun 25 years before getting dies. At the time I was in the mood to order, Dave Davison was either passing or had just passed and things at CH4D were a bit unsettled. Whiddon could supply the dies in several months at almost twice the money. I think they quoted me 6 months I had them in 3 months. Like I may have already said the Whiddon makes some incredible tooling.
For the first 25 years I used other dies to load my cartridge. I think I used .416 Rem Mag dies. They would size the neck just fine, but not the body. But that was a while back. I would have to go dig the cases out but I believe I started with 300 Win Mag. Later I know made some cases from .375 H&H cases.
One thing I learned was that the .416 Taylor cartridge would fit my chamber. My loaded rounds would fit the Taylor chamber, but only with extreme difficulty. Taylor cartridge had a minutely smaller shoulder diameter, all else appeared the same. Sizing my fired cases in a Taylor die showed some distinct resizing on the shoulder diameter. I chose not go that route as I didn't want to deal with excessive resizing on the shoulder.
The .416 Taylor was originally the .416 Chatfield-Taylor. Chatfield being the originator. Barnes-Johnson proceeded Chatfield by several years. I do wonder.
Here is a photo from my copy of Ackley on your cartridge. Something to keep in mind about Loads in Ackley, you should always treat then as Maximum and reduce to start.