Major home improvement stores such as Lowe's and The Home Depot sell ventless gas logs as of 2015. Private sellers on Amazon.com also sell logs. Local gas appliance dealers such as Blossman often have a selection of logs available as well.
Ventless gas logs come in a variety of sizes to fit different fireplace inserts. Woodlanddirect.com carries gas logs that have the appearance of oak, sassafras, ponderosa, or hickory logs burning.
Local hardware stores sometimes have logs for sale on a seasonal basis. Majesticproducts.com makes ventless logs that are hand-painted for a more authentic look. Wal-Mart offers logs for sale both online and in-store on a seasonal basis.