Like Seager, Kershaw has an officially licensed Baseball card while he was still in high school. He was a member of the Team USA Junior National team, so Upper Deck included him in a box set they release in 2005. They were initially sold as a complete 25-card set and included a random autograph card, a game-used autograph jersey relic card, a dual signed autograph card and an insert card (a "Vision of the Future" acetate card).
Check out all of the available Kershaw cards in this set below. BTW, there are several different variations available for each of the autographed cards based on the color of the ink he used to sign them. They come in black, blue and red. Also, I seem to remember there being green ink cards, but I have yet to find a good checklist indicating that.
UPDATE: I thought I would add that his teammates on this team who also made it to the Majors include Brett Anderson, Greg Peavey, Shawn Tolleson and Bellin Betances.
2005 Upper Deck USA Junior National Team Box Set
Base Card #86 Clayton Kershaw