Does Oko, Thief of Crowns come in a planeswalker deck, or only as an individual card?
It's 'just' a regular Throne of Eldraine card, found in boosters and tournament packs – if you're lucky, of course; those cards are always random.

There is a preconstructed Throne of Eldraine deck with an Oko planeswalker, but it's Oko, the Trickster. You can find those decks e.g. here.