Nyko's support for the Nintendo Switch has so far been incredibly strong. They've offered charging solutions for the Switch and Joy Cons and even a portable docking kit. Now they are offering the Core Controller, a traditional gamepad that should meet your needs for the bare essentials.
The Core Controller is just that--a no-frills wired usb gamepad. It offers the same layout as the Switch Pro Controller, and features a 10 foot cable and programmable turbo and auto-fire functions. It is also compatible with your PC through USB so that's a plus. The Core Controller is only $20, a fraction of the expensive $70 Nintendo Pro Controller, but with the lower price you're missing a few features. The Core Controller does not contain an NFC reader for Amiibo, gyroscope motion controls or any rumble feedback to speak of.
For this reason it sounds like the Core Controller is the best option if you want to fill out your gamepad selection for some quick Mario Kart without breaking the bank. Check out the video below for more info.