Nope, Apple don't do one and there aren't any third-party adapters. Typical huh, they bang on about Thunderbolt for ages and then drop its support with the new USB-C ... but anyway.
I think what you'll have to do is a Thunderbolt>HDMI adapter on the TB display, then a USB-C>HDMI adapter on the MacBook, and then an HDMI cable to hook the two up.