Many entrepreneurs including photographers use SQUARE to process credit card payments for their clients. I am one of them, and I carry my SQUARE CARD READER with me all the time. I wanted to find a little pouch to put my SQUARE CARD READER, so it won't be damaged inside of my purse or shooting bag, but didn't want to spend a lot of money for it. After browsing through Etsy, I decided to go through my house to see if I already have something that works for this purpose...and voila! I found something good. :)
It is a Nike+ sensor pocket that you can attached to non-Nike+ shoes, and it is made by a company called Nathan Sports.
What's great is that this little pocket has a long Velcro that goes around the back side, then go over the flap and secure it to the bottom of the front side. I can use this feature to attach this pocket securely on my shoulder strap of the shooting bag, or purse, if I wanted to have an easy access to the card reader.
You can find more information about this product here: http://www.nathansports.com/gear/performance-gear/shoe-pocket-plus
I got mine at DICK'S SPORTING GOODS - click here to see the product on their site.
Have a great day, and happy swiping!