How to buy something from the Mann Co. Store
Solution 1:
When you go into the game, Press: Mann Co. Store. You can buy lots of cosmetics there, To make sure you buy nothing of the Market, look for stuff such as: Buy in market or Price in market. If it doesn't have a "Price in market", or anything similiar, you can't buy it in the market. So then you can buy it from the official Mann Co. Store.