Get a Motorola SB6141 cable modem for $52.99 - CNET
Best Buy: Motorola SURFboard eXtreme Broadband Cable Modem SB6120
Motorola MB8600 Ultra Fast Cable Modem, DOCSIS 3.,1 Plus (32x8) DOCSIS 3.0, Certified for XFINITY by Comcast, Cox, Time Warner, & More, 1 Gbps Max Speed - Walmart.com
Time Warner Cable Modem Motorola SB6121 TWC Approved
Motorola's DOCSIS 3.1 Cable Modem lets you ditch the rental at $133 (Second-best) - 9to5Toys