Why the snark? It'll probably take a year before you can get a cheap throw-away mouse with USB-C at Staples or Best Buy.
But assuming you're a professional, you either already have a bluetooth mouse/trackpad or you'll want some quality and order a mouse from a reputable brand.
Heh, that's an interesting point you make. Assuming you can't or don't want to use Bluetooth, I was surprised to see that in The Netherlands, there's only 1 brand that carries an USB-C mouse, and it's a budget brand as well:
http://www.trust.com/en/product/20969-usb-c-retractable-mini...
So I have to admit it's indeed very, very slim pickings.