OTG Pendrive

If you want to buy a pen drive only for your mobile phone I recommend you SunDisk 3.0 otg pen drive which will connect directly to your mobile phone and then you can store anything in this pen drive.

In the field of storage device, SanDisk is the best company, that's why I recommend you if you want to buy a memory card SanDisk memory card or Pendrive. 

I am providing a link to buy one. This variant has dual connection with 128gb storage capacity.