Thank you for responding!
It took me a really long time to find the game, probably several hours altogether.
You’re right-finding pieces are very rare, and usually if I find a piece in stock on Historical Board Gaming, I usually just buy the whole stock (at least as much as I need, which is usually more than the available stock). It’s sad though that the extra pieces needed the most (infantry and artillery) are the ones that are the hardest to get. The hardest pieces to get are German (although I rally want the Ottoman ones for the unique colour which is irreplaceable by World War 2 pieces), and the easiest prices to find are American. These is my personal findings, and I might be completely wrong.
Keep looking and you will be able to find it!