My Smith always makes my dies when he builds the rifle using my reamers. Is not a big deal at all for a good Smith to do just takes time and money but it is worth it esp for my competition rifles. Then I have sporters built in the same chambering using the same dies...
The seating die on my 338 Slowpoke is a regular Wilson 338 Lapua just made a little larger! The sizing die is the only challenge because carburizing is involved and a lot charge can be expensive.. Picked up many dies in the past from being carburized (tried to wait until the shop was making dies then have mine done so as to avoid the lot charge) and took them back to the shop for polishing and assy. I use Newlon blanks in 12L-14.