King-sized fitted sheets are readily available online at sites such as Overstock.com and Amazon.com. They can be purchased from many traditional brick and mortar retailers also.
An advantage of shopping online for sheets is that most items listed have reviews based on consumers' experiences, listing the pros and cons of the available items. Another plus of online shopping is that the prices are typically lower than those in stores due to much lower overhead costs. Overstock.com offers free shipping on purchases over $50 as of August 2015. Amazon.com offers free shipping on purchases over $99. Both sites allow product searches based on chosen criteria such as full sets versus single pieces or thread count.