Dia
Hardware store, or you might have to have it made special for you. :)

ansmenam
You said you didn't want wooden so have you ever considered decals? Follow this link. They have many different size options from 1 inch to 22 inches, color choices, as well as lettering style. They look really good when applied.

Miss Ann Thrope
Try urbanoutfitters.com or homedepot.com

matt
Gordmans has many types of what you are describing, and at a discounted price too. this is only going to help you if you live near one though...

me
In Gold Acid etched Wrought Iron Chromes and LEDs

Svetlana
See this SOLID LETTER B - Blue or more