If you’re looking to buy a copy on eBay, search for “World War 2 the Expansion”. There’s also “World War 2 Expansion 2” and “World War 2 Expansion 3” available for purchase on eBay. The rules you want are in the first book/set.
The Exp2 changed up the generic square chit counters for Cruisers, Destroyers, and Escorts for color-coded round counters (and changed a few other things). The Exp3 featured a new map and a lot of new counters for new idea (pill boxes, variable IPC values for Japan/USA islands in the Pacific, special Naval/Carrier Fighters, etc).
Yes, I have all three. EBay is not quite your friend but can be useful if you know what you’re doing.
-Midnight_Reaper