Petty Graffiti OP-1 Medium stand.
A hollowed out version of the original and little beefier than the minimal.
You will need to order TWO of these (one for each side) for the stand to be functional!
I suggest ordering two bolts form www.boltdepot.com product #6685 to attach it to your OP-1. You will need an allen wrench (Ikea style, looks like an 'L' ) to secure the bolt in place.