In my state you can get them where you get your license tags/plates for your automobile.
Of course you need something in writing from your doctor stating why you are disabled first.
You should be able to go to your county tag renewal website & download an application for disabled tags/stickers and take that to your doctor, then when he's completed his part, you then take it to the tag office.
At least that's how it works here.
As for getting a disabled parking spot at the local WalMart, I say forget it....they're always full when I want to park there.