The staff at the big box stores seem not to know what they are. I've found them in two places at Lowe's: in the tools section near the welding supplies and in the plumbing section near the stuff for sweating copper pipe.
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Oxiclean will do the same level of cleaning but it lacks the "wetting agent" that PBW utilizes.
I use a thermapen. It's a hundred bucks, but it is worth the expense.
I am getting some oxidized notes in my last brew and am trying to figure where in the process that happened.