There are such devices, because I have one.
But you do need a card reader too.
The device I have will let you copy files from
a USB device to a USB device.
So I plug in the card reader to the input USB port and a flash drive to the output port.
It is made by a company called i.Perris
Here is their website:
The place where I bought mine, no longer handles them.
But their website shows places to buy their products.
The device I have is called:
OTG Photo & Data Transfer Bridge - Model No. 103
It runs on 3 AAA batteries.
I want to travel light and need a way to get my photos from a memory card [SD] to a flash drive without having to load them onto a computer and then download them to the flash drive. Any ideas?