If you purchase a new one from sharper image, and can identify the part number for the power adapter, there are many sharper image power adapters for sale on ebay and other sites, but without knowing the correct part, it is difficult to identify it only by 201791 which is the foot massager model itself.

https://www.sharperimage.com/si/view/category/Search/100209?trail=SRCH%3A+201791+

You would at least have a working model, and could take your time searching for a replacement charger.

I have to assume that you contacted Sharper Image to ask for assistance already.

Order it directly from sharper image.