There are websites that create and sell custom logo printed shopping bags, such as uline.com or bagsandbowsonline.com. These bags can be as simple as plastic t-shirt bags, small party favor bags, or if the buyer is interested in paying more, larger paper shopping bags.
Websites such as uline.com and bagsandbowsonline.com allow their buyers to order factory-made custom shopping bags with the desired logo on them. These bags are sold in bulk to retailers for the use of their own customers.
Companies do not sell these items in retail settings because creating patterns for single or very few prints is not economically sound, and they would have to charge an exorbitant fee to offset the costs. There is also not much of a market for single custom bags, so buying a small number of these bags with a unique custom print on them is nearly impossible.
If someone wants to make an individual bag, they may be able to use public printing equipment at a printing shop. They would need to learn how to use the equipment and make the pattern themselves or hire someone with the knowledge, a service usually provided by or required by print shops. They can then take the pattern and stamp it onto a blank bag. This allows the person to create as many or as few of the bags as they need if they have no need to buy in bulk.