I have purchased the official BlackBerry KEYone dual layer case, and also a cheap slim black case from a mall kiosk. Ironically, the mall kiosk case actually has better grip and is slimmer, and was only $15. After some research, it turns out that the mall kiosk was selling this case that Best Buy Canada also offers:
https://m.bestbuy.ca/en-CA/product/l...black/11456505