xb6 battery backup

I have been trying for over a month to order a battery backup for my Arris 3482 xb6 modem.  Three times I have been promised delivery in 2 to 5 business days with nothing happening.  Twice I have been told that the modem can't be shipped and must be installed by a technician and a service visit scheduled.  Both times just before the visit I received a phone call from the tech telling me that no such battery backup existed.  Has anyone had this backup delivered or installed recently?  I understand the current part number is Arris XBB2-4A and the cost is $165.  The discontinued XBB1 is available new on ebay for $30.