I use this one and haven't had any issues:
https://www.amazon.com/gp/product/B01I5TJGSE/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1
NETGEAR DOCSIS 3.1 Gigabit Cable Modem. Max download speeds of 6.0 Gbps, For XFINITY by Comcast and Cox. Compatible with Gig-Speed from Xfinity (CM1000)