Milk and lemon juice is not actually as great a substitute as people think it is. It's known as acidulated milk, not buttermilk, and it doesn't have the flavors or tenderizing aspects of buttermilk and other fermented/cultured milks.

Try mixing sour cream or yogurt with milk instead… or just get some buttermilk. Smaller cartons are not so hard to find, and using up buttermilk is a lot easier than people think. Pancakes, waffles, (southern US) biscuits and so on, of course, but also breading for friend chicken or fish, as a drink, a soak for beans or rice, the liquid for stuffing, etc.