Did you read this?
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Stiletto is a UK registered business with all manufacturing and exports taking place from the UK
That means it'll never be available for import, unless an LEO/GOV contract wants it.
But there is nothing stopping anyone from making their own. You can get tungsten welding rod from various places pretty cheaply if you're just wanting to load up a few mags.
Just be sure not to shoot it from a pistol. You can only shoot it from a carbine/rifle. Legally.