Customer-owned CableCard?

For years I've used a Cox-supplied CableCard and Motorola tuning adapter for my TiVo whole home system. Works great. I'm thinking of adding another TiVo unit and was wondering if Cox will authorize (pair) customer-owned Motorola/Arris M-Cards and tuning adapters. These parts are next to impossible to get at Cox stores but dime-a-dozen online.