There are no official merchandise yet. But there are several unofficial. Here's one of them by @craig-grant .
Where can I purchase 'official ' trademarked Steemit merchandise? / 7-23-2016 / @craig-grant / https://steemit.com/steemit/@kakradetome/ https://steemit.com/steem/@craig-grant/you-re-not-official-until-you-have-your-steem-merchandise-on-deck / Steemit merchandise

PS: @craig-grant is a magic spaceship human being :) Much love @craig-grant :)