Chainsaw sharpening tools are available at major home improvement stores such as Lowe's and Home Depot. Equipment dealers also carry sharpening tools. A Husqvarna or Stihl dealer typically has sharpeners for sale for a variety of different chainsaws.
Local hardware stores carry files for sharpening saws. Farm and garden supply stores also often have at least a few types of files in stock. Northern Tool sells files and sharpeners. Major dealers and home improvement stores often have complete chainsaw sharpening kits available. Make sure that the right size file is purchased for the model of chainsaw it is to be used on.