As stated in this thread:
You can call the Fiber Solution Center if the battery is within its one year warranty period, or check out Radio Shack, Home Depot, etc. The 12 volt 7.2 amp-hour battery is common to other devices such as alarm systems, and is a common size. Electronic specialty houses such as DigiKey and Mouser would probably also have them.
Shop around. See what Verizon will charge you to replace it, versus how much it will cost you to obtain a new one from somewhere else.
Hope this helps.
Written by J.M. Culbreath - John L
Last updated on 11.08.07