Amazon is selling the Linksys High Speed DOCSIS 3.0 24×8 Cable Modem, Certified for Comcast/Xfinity, Time Warner, Cox & Charter (CM3024)
Free 2 Day with Prime, of course.
When I checked eBay, I’m seeing refurbs on this model going for $60. It looks like Square Trade is also offering 3 year protection for $1.21 via the Amazon link, if that’s important to you.
Definitely a better option than dropping $10/month for modem rental.