Buy the pass individually via the Nintendo eShop.
If the content doesn't appear, visit the eShop, select your profile, and go to "Redownload" to trigger the DLC install. Download File Mario Kart 8 Deluxe [DLC] [010015...
Includes classics like Coconut Mall (Wii) and Waluigi Pinball (DS). Buy the pass individually via the Nintendo eShop