Gateway Purchase

If I am in an area that is currently served by the XB8, is it possible to purchase one outright instead of leasing one?  My mother is currently in such an area, is a senior citizen, and is actually still using the voice services, but her current gateway, a Netgear CM1150v, is starting to have issues.  The XB8 and XB7 have the Voice-Only backup battery option, but I cannot find either available for third-party purchase.