I've looked too and not found a good dual SIM option that is an unlocked world phone. I've really got my eye on the new OnePlus One phone being released next week though. Given the speeds of GSM 3G I am not that concerned about having LTE worldwide especially since the tmobile plan caps those speeds anyway internationally. Though the OnePlus One seems to have most LTE bands covered though. Not dual SIM but for what that phone offers I am ok swapping sims if needed.