I read that Kings Bay cost the US taxpayer over $ 5Bn dollars in 2017 cash terms for the base alone. You'd have to buy the boats from the Americans (doubtful), the Brits (impossible) as they can't build fast enough) or of course the French . Interestingly the Brazilians are building their own SSN with French help but it was laid down in 2017 and isn't expected to be launched until maybe 2030.... notional cost for the vessel alone is $ 7.4 Bn