Remington sells the Zastava-built Mausers (from former Yugoslavia), and the actions have been imported over the years by several different distributors. Interarms and Charles Daly are two that come readily to mind. You may be able to find a new, old-stock (NOS) Mark X Mauser action, as they were called. I don't think Remington is importing just the actions.
Other than that, you're either going to have to buy a complete rifle (Remington M798), or go without. FWIW, many custom rifle builders have stated over the years that making a good milsurp Mauser into a really nice rifle is easier than doing it with a Zastava action. The better milsurp actions are smoother.