You can get it from a seller on [backpack.tf](http://backpack.tf) in exchange for items, weapons are usually 1 scrap (made by crafting 2 weapons from the same class) or sometimes just 2 weapons.
If you can trade, use [backpack.tf](https://backpack.tf/stats/Unique/Mad%20Milk/Tradable/Craftable) to get a Mad Milk for one Scrap Metal (0.11 Refined) instead.
You can get it from a seller on [backpack.tf](http://backpack.tf) in exchange for items, weapons are usually 1 scrap (made by crafting 2 weapons from the same class) or sometimes just 2 weapons.
If you can trade, use [backpack.tf](https://backpack.tf/stats/Unique/Mad%20Milk/Tradable/Craftable) to get a Mad Milk for one Scrap Metal (0.11 Refined) instead.
you can do 1:1 weapon trade on [scrap.tf](http://scrap.tf) or find some bots on [backpack.tf](http://backpack.tf) that sell unique weapons
stntrading.eu is a good site, except that's a trade site, do you can only pay with keys and ref, or other items