Is there such a thing? Where would a guy find 28 30 brass these days?

6x70R can be used to make 28/30 Stevens but, it’s hard to find.  Ledball

Last year I bouight some original .28-30 on Gunbroker, but I paid over $5 per piece.  Only time I've seen any in the last decade or so.

Rocky Mountain Cartridge will machine some for you, but it will also be very spendy.    

As Ledball posted, 6x70R will make a passable case. The base diameter difference is .347 vs .355 for a fired UMC case I'm holding in my hand.  Several years ago I bought and shared out the last that Huntington's had. Haven't seen any more since, but haven't been looking, either.  

And then of course there's Bertram, if anybody has any.

All I know.  

N.B. dies.  CH4D will make you a set, but the expander plug they supply is too small and much too short.  It allows the case to cock in the shellholder and expands off center.    Here is a set of tools I made for a friend up in Michigan.  They fit into a Lee "universal expander" (which it's not) die body.  The two parts at the left are the expander and the spacer that positions in the body.  Center is a neck resizer, on right are seater parts.