For a local source, I like Trippy's Uniform Supply in Shrewsbury, across the street from The Gun Room on Rt. 9, or, if you don't mind buying off of the Internet, my favorite source is www.dtdistributors.com. I have purchased at least a dozen cans of OC spray from them over the years. Very reliable, fast shipping, no hassles.
The stuff that the major retailers (and most gun stores) sells in these parts is NOT a good solution!
Try police supply stores for "the real stuff" . . . and you need to buy in containers bigger than a lipstick case for it to work enough to get your ass out of there. The tiny containers are woefully inadequate.