My local Lowes has plain "Crown Brand" 31% MA in the paint section for about $8/gal.

They also have 2 gal boxes of Kem-Tek MA, but I haven't read the label on those, so I'm not sure about them. However, the MSDS sheet indicates that these are just a 50:50 dilution of standard MA, and would be fine to use. The 15% strength acid barely fumes, so it's easier to work with . . . but you STILL need gloves and glasses, and STILL need to read the MA page: http://pool9.net/ma/