The .30 Krag is not one of the standard offerings from Lee for their collet neck sizer, but they will make you a custom one for only $70. I bought a collet die for a .300 Win Mag rifle I inherited, and it makes sizing trivial. I'll get a Krag one this year.

An alternative comes from Redding, who make hardened neck sizing rings. They are in 0.001" increments, so you can match the amount of sizing your brass needs. There is no expander ball. They offer a .303 body (no .30 Krag), but I think the appropriate ring in that die would do. These aren't cheap, though, especially when you'll want to have several rings to accommodate the differences in case neck thickness among lots and brands. See the S dies on their site.

Hornady makes a generic .30 neck sizer. I've used mine on both the Krag and the .300 WM. It has an expander ball. It is inexpensive. With a good neck chamfer and boat tail bullets, I image you could work without the expander.

   Karl