I've just read this months issue of SFX magazine and the interviewer mentions that they are wearing a Groverfield shirt and JJ asked them where they got it.
I've pimped the HE site on their forum in relation to this so I hope it's the same shirt.
I could scan it but there's not much to see, I quote -
"For the last couple of years he's been juggling multiple projects while also aiming to do one of the toughest jobs in SF - reinvent Star Trek while keeping true fans happy. For now though Abrams just wants the shirt off our back. No, not literally, he's just delighted by SFX's "Groverfield" T-shirt when we meet him to talk trek in an upscale LA hotel." By James White, SFX's LA Editor.