The reasonably priced Lee 'universal expanding die' uses a pair of tapered, reversible 'slugs' inside. A number of useful reloading tool slugs can be turned on a lathe to replace them in the die body, including a powder compression plug. As said, if you have an M die you can make your own too, but the Lee is just a simple turning with no threaded shank.
FWIW, The 'powder through expanding die' in the Lee die set is the same die body with the same potential.