#1 - Dec. 18, 2012, 1:20 p.m.
Players wishing to acquire a Battle.net Authenticator have several options. The Battle.net Mobile Authenticator is available for many types of smartphone, and you can find out more about it here. For many people, this is the easiest and cheapest option!
If you prefer to have a physical Battle.net Authenticator, you can get hold of one from several sources including the online retailers and high-street stores listed here.