where can you purchase "almond butter"?
I get it at Trader Joe's. Do you have a Trader Joe's near you? I imagine a health food store would have it as well.
I usually find it at health food stores and Whole Foods.
Regular grocery stores also carry almond butter.
If you can't find almond butter, peanut butter or cashew butter would also work.
If you have a food processor, making almond butter is very easy. Roast whole almonds at 350 until they smell toasty, about 10 minutes. Cool them down until warm, put into food processor, and let it go - it will take a while, first becoming mealy, then pasty - I usually stop when the oil starts to exude or separate. If you want a smoother texture, which you might for a recipe such as the granola bars, you can add a bit of walnut oil or a neutral oil like grapeseed, canola, etc., while the processor is going. This works for all kinds of nuts and is delish.