Brownelle's has them in stock, though they don't note the Mod 30 in particular... They do look to have all three sizes of the standard plastic guns though... Funny thing - Dillon used to carry them, then carried a generic version.
I had a Don Hume for my plastic - if MS is Grade A, i'd say Hume is a "C". Passable, but nothing special - however, the price reflects this fact.