I don't think a retro fit is available as there is no 'kit' for an upgrade from Astro to Clipper or POF option on the Astro (or raven).
The floats need the inflation system (bottle & valves under LHS F seat); changes to the collective for the trigger mechanism; pipework; complete new skid system with floats on (this is the easy bit); tail rotor protection stab (extra bolting which might mean a whole new tail section because the stab I think is not a 'kit').
The whole M&B changes with this so the aircraft needs re-weighing and certifying. If not based on std parts that can be added on I think this might make it a new aircraft so you might need to get the whole thing replated as a new mark of aircraft.
'More than the average bear' as Yogi used to say. h-r
But things might be different outside of the rarefied atmosphere of JAR-land.