Our Walmart started carrying a small bag of DE in the pool section for the first time this year, but I haven't seen it in stock since the beginning of the summer. Lowe's and Home Depot carry it around here.

For MA, don't know if you have a Tractor Supply Company store near you, but they're the cheapest place around here. Many hardware stores also carry it in the paint department--Lowe's and Home Depot included, although they value theirs highly

Janet