CH4D makes a set they call the .375-444 which I use to load for my .375 JDJ. I haven't had any trouble with them, but if I had to do it over again I would just get them from SSK. Only about 10 dollars difference between the two.
I think Pacific Durachrome also made them as I have seen some sets on e-bay, but that would have had to been a LONG time ago.