That recommend makes for a
provocative probe. On the one hand, it makes the listener (or reader) plot out local milk purchasing locales (groceries, gas station marts, etc). On the other, it lets us wonder about what sorts of places don't have ready milk access - milk deserts?
On our homestead, we pass the test twice.
First, we milk our goats, when they're lactating, so a supply is literally ready to hand. It's goat milk, which isn't to everyone's taste, but certainly serves our purposes.
Second, we can drive to our town's general store, the Ripton Country Store. It has plenty of (cow) milk. That's about a 10 minute drive, mostly along the very rural Ripton-Lincoln Road. It takes two of us about 30 minutes to bike it, when the roads aren't lined with snow and ice.
If neither are available, then it's a 30 minute drive to either nearest town, Middlebury or Hancock, down and/or up very steep mountain roads.