Don't know where you can find it in Dubai, if you can order online that's probably your best bet. I don't know if Best Buy ships to Dubai or not or if they will even sell you the phone without a contract.
You don't need to buy a pre-unlocked one either. there are many third party companies that unlock phones.
cellunlock.net is one, there are others. Once you get the Tour and unlock it you can use whichever GSM provider you want. Just be aware you need to get a BlackBerry plan if you want the data to work right and you have to follow directions about activating it on a GSM provider.
I have the Verizon blackberry tour in dubai on etisalat, and it rarely works. When I call people on DU and some on Etisalat a message comes up saying number unobtainable. Also, I rarely get connection to the internet. I have the unlimited domestic plan. What network settings should I use, or is the tour only compatible with du.