Other than the usual advice of looking around, ebay,etc. I have had dies honed out by a gunsmith to a slightly larger size. If it is too much, a new punch (Whatever you call the thing in the middle that goes up& down?) would have to be made.
As for top punches, I now have about 6 or 8. I don't get new ones, 'cause i can usually find one that will "do".