Utility bike bicycle trailer. Connects to bike seat post. Sized to hold a cooler, shown in picture, however not consisted of.
This is the trailer: https://cycletote.com/shop/small-utility-trailer/ which costs $399.
The trailer is missing the hitch, which costs $25. I didn't wish to buy it since it is available in various sizes, depending on the size of your seat post. Here is where you would purchase it: https://cycletote.com/shop/hitch/.
Also, requires inner tubes patched or changed.
If you are interested, Email. Found in Denver Five Points location.