If your device doesn’t support USB OTG, then buying a flash drive with a microUSB port is pointless. However, if your phone does support USB OTG, then it’s a nifty way to .
Going online to buy USB flash drives is by far the best way to go. For one thing, the selection available online far outshine anything available in retail. On top of that, the prices are better (especially if buying in bulk) because the retail markup is removed. There are shipping and handling with some companies, but those charges are generally very affordable.
Another way to save money is to consider buying used flash drives for everyday use as well as in order to benefit from the many ways they can be used. There are a couple of things to keep in mind when buying a used USB flash drive, but by using appropriate caution and by taking the necessary steps to ensure the safety of the device once purchased, most users can find real value by purchasing used USB flash drives.
You can buy a flash drive just about anywhere. I got mine from Walmart. It's pink and I think its an 8GB. They are really reasonably priced. I've even seen some at CVS and Walgreens but I probably wouldn't get one from there.