Depends on the BORG. The Lowes at 40/42 does not stock 1/2". The HD on Timber Dr. does. I would check both BORGS in your area. If one does not have it, the other likely will.
HD is your best bet for "good" sheet goods (½" MDF, Melamine, hardboard). But if you want "professional" stuff look to Raleigh Hardwoods aka Wurth Group, or Horizon Forest products.
The Raleigh Hardwoods aka Wurth Group has 1/2" thick MDF, but only in 5x8 sheets. I went over there looking for some just a few days ago, but alas, I can not get 5' wide pieces in my car and had to pass. The Apex HD has 4x8 sheets.
Thanks for the replies. I had looked at one Lowes and the only had 3/4 so I just assumed that that was the normal situation at all locations. Lesson learned ... no two stores have the same stuff.