I am confused. The picture provided for AC adapter 43NY4 is the correct AC adapter for that system?
Inspiron 7778 AC adapter list =
43NY4 65w, 19.5v, 3 Pin, 4.5mm, C6, Delta
MGJN9 65w, 19.5v, 3 Pin, 4.5mm, L6, Liteon
G6J41 65w, 19.5v, 3 Pin, 4.5mm, C6, Chicony
0285K 45w, 19.5v, 3 Pin, 4.5mm, C6, Chicony
Pictured AC adapter is the adapter that came with it and works fine. I am looking for a spare to use for work/travel. I cannot find 43NY4 (or any of the other adapters you listed) for sale at Dell, only on third party sites (which are probably fake based on price point alone).
I check Amazon and look at the sellers reviews. Here is one, 3.5 stars out of 5.