Does that even exist?? It's a straight walled case. I would expect neck sizers to only be made for bottleneck cases. You could look to see if Lee makes a collet die that will suit your needs.
Could be made easily BUT would need to know the outside dimension of a loaded round, neck wall thickness, and bullet diameter, along with desired neck tension.
Hard part is the changing nature of brass as it work hardens.
I made a similar die for 45 Colt. Got a little larger and neck tension sucked. Need to remake that, it sure was easy on brass.
Not sure about neck sizing, but when I got a set of the RCBS Cowboy dies rather than the standard older RCBS dies, it made a world of difference in my .38-55.