I just took the 50' RG6 cable that came with ours and bought a second one at Home Depot and used cable ties to put the two together. I just roll them both up and store then when we travel. Since I only use the power cable to set it up then store it I am not worried about it being connected to the RG6 cables. I doubt you are going to find a dual RG6 setup with the power cord combined with it. Just a quick search came up with this for a dual 50' RG6 cable.
http://www.ebay.com/itm/50-ft-DUAL-RG6-TV-cable-w-Ground-wire-BEST-QUALITY-coax-3GHz-solid-copper-UL-/380480484829