There is a Dick's and a Sports Authority a couple of miles from my house and neither carries much in the way of umpire gear. Certainly no pants or shirts, but if you need a plate brush or indicator you're in luck!
There is one small, family-owned sporting goods store a couple of more miles away that used to carry OHSAA-logoed uniforms, but they seem to have stopped carrying these a few years ago. And their prices were about 25% higher than the on-line stuff you can buy.
I'm also fortunate to have a dedicated umpire supply store right here in town, only about a 20 minute drive away. Nothing like trying stuff on before you buy it, or being able to get a needed piece of gear in a matter of minutes.
They also do internet sales. here is a link to their website:
http://www.refandsport.com/