NewEgg has the Motorola MB86000 DOCSIS 3.1 for $129.99 with free 3-day shipping or shoprunner if you have it. Cheapest price I could find on a DOCSIS 3.1 modem at the moment. These aren’t the old surfboard line as those are moved to Arris, but are produced by Zoom.
Use promo code 91PCGD32 for $29 discount.
https://www.newegg.com/Product/Pr…-_-Product