Try Simplex Australia HS
Their die list is actually more than what is displayed - yes they even make 577/450Martin Henry as well & they are very well made indeed, I know I have a set!
So give them a bell mate - more than worth a try

Contact
02 9758 1280
ssimple2@bigpond.net.au

Basic Die list
http://simplexreloading.com.au/die-list/