I wouldn't base your search around locating an unlocked device. You can easily get the device unlocked yourself through any number of third party services. Horizon Wireless is a sponsor on this site and you can get a member discount. Just try to find your best deal. Unlocking will only run you $20-40 depending on who you go through.
I would also read this if you're considering going through eBay or craigslist.... to be sure you don't get taken for a ride..... Buying a BlackBerry off eBay - BlackBerryFAQ