I was looking for this at the local Lowe's, Home Depot and Menards just a few weeks ago as I use TSP to clean walls prior to painting.
None of the three had it on their shelves, the Home Depot near me told me it's not sold anymore due to EPA regulations. If you have a "source" near you, can I paypal you some money to get it and ship it to me?
Even Google Product Search show’s it’s not available anywhere near me. But then, I can buy it online or drive 55 miles to the nearest retailer that still sells it (sigh, this government is making it so hard to do anything these days. What used to be a simple trip to the local Ace Hardware now requires an internet investigation!)
Check neighborhood hardware stores, Sears, paint stores, farm & ranch stores. It’s still around. It can be purchased online too.