What is nice about the Historical Board Gaming site is that you may order supplement parts from many different versions of Axis and Allies. I currently own a copy of Axis and Allies 1941, but I was able to add some unique pieces to my game from different versions of the game.
I made the order to obtain several sets of dice for other games, but since Historical Board Gaming were offering some of their parts on sale I decided to purchase a few of these game pieces. Some of the more unique pieces that I purchased were a set of American WWII P-38 fighters, several Liberty transport ships, and a set of Japanese Type 95 ha-Go tanks.
These parts will be a welcome addition to the game, as the game no longer provides enough pieces to go around. Instead you must use markers to represent multiple pieces. Markers are a good thing in that they keep the very congested board from becoming impossible to work with. However, it is still nice to have additional pieces to pull from, when the need arises.