There are currently two devices that support the new USB-C port, and those are the 12-inch MacBook and the new 2015 Chromebook Pixel 2. However, because this port is so new there are not too many accessory options, although Belkin and Google do have a few accessories for you to choose from, and we suspect others will follow shortly.
Google and Belkin USB-C cables and adapters — What we like about these options is that the prices are lower than Apple, although they currently have a small range, unlike Google and Belkin, with the latter having the most.
There are some other third-party accessory makers offering USB-C accessories, which you can see by simply running a search on Amazon.com.
With Google they do have a pretty good selection, which includes a USB Type-C to USB Adapter for $13, USB Type-C to USB Cable also for the same price and even Universal Type-C Charger with a 12-foot USB-C cable for $60.
As for Belkin, you also have a pretty decent choice of cables, such as USB-C to Gigabit Ethernet Adapter, USB-C to standard USB Adapter and even a USB-C-to-USB-C Cable. You can find the full list of cables and prices at 9To5 Mac.