I'm not sure if this is what you're looking for, but if you couldn't find an escrow platform, try asking out on OpenBazaar's slack channel:
http://slack.openbazaar.org/Maybe the mods/admins might be willing to help you out in finding an arbitrator. Then again, I'm not guaranteeing that they're gonna help you. Just giving you a heads up if ever you still couldn't find what you're looking for after a few weeks/months.