Easier than you think. You can make your own.
Check this out and see what you're missing out on.
What you will need:
4 1/2 cups milk total
Skewer stick made of wood
See below for Instructions:
In a large saucepan place 2 cups of milk in the pan. Add the skewer stick to the pan standing straight. Mark off where the 2 cups ends.
Add 2 and 1/2 cups more milk. Bring to a boil and then down to a simmer, until it boils down to reach that 2 cup mark on your skewer. That will have reduced the milk to 60% which is taking out the water content. That's how you know your milk has evaporated correctly.
Keep skimming off the top if a film forms.
After it reaches that 2 cup mark strain it and store in the refrigerator. This will stay fresh for 1 week. It makes 2 cups.