As of February 2015, Crock-Pot slow cooker liners can be purchased online at the official Crock-Pot website. They can also be purchased online at Amazon or at a physical Walmart location.
Amazon also carries other brands of slow cooker liners, including Reynolds, Pan Saver and Kitchen Collection. Amazon offers free shipping for orders totaling at least $35. Items sold by third-party vendors may or may not ship free. The Crock-Pot website offers free shipping on orders of $49 or more.
Walmart does sell Crock-Pots online, as do Amazon and the Crock-Pot website. Other brands of slow cookers offered by Amazon and Walmart include Hamilton Beach, Cuisinart and Farberware.