Well to be honest I'd rather make it myself, if you can find a good recipe then you should tell us about it. Also considering how much it costs to get old comics shipped over the Atlantic I dread to think of the cost of getting a crate of Nuka-Cola sent over, hell I don't even like Cola that much, I just have Ginger Beer....
well my nuka cola is simple to make
get 1 pepsi 1 coke 1 sprite. mix all 3.
then get some hot sauce (any kind will do) and put around 10 drops in.
the cut a lemon and lime in half and sqeeze every drop out of them into the mixture and stur for 10 seconds.
there you go a Catfish Nuka cola.
(warning not tested. do not give to elderly or young children as may cause severely odd looking faces that may be permanent)