As of 2015, find putting green grass seeds online at Amazon.com or Outsidepride.com. Hancockseed.com also sells putting green seed. All of these sellers offer a variety of grass seed, including Bermuda grass.
Amazon.com has several varieties of putting green grass seed available including bentgrass and zoysia. In addition to the seeds, Amazon.com also sells fertilizer, sod and potting soil for putting green grass. One nice feature of buying from Amazon.com is that it is possible to refine search results depending on the growing zone.
Outsidepride.com also has putting green seed available, and it comes in a variety of brands and varieties, including Crystal BlueLinks creeping bentgrass, Penncross creeping bentgrass, Princess Bermuda seed and Pure Select creeping bentgrass. Depending on the brand, the seed is available in bags as small as one pound all the way up to 25 pounds. The website also sells products that aid in the growth of the seeds, including LazyMan Soil Doctor, which is a liquid aerator, fertilizer, dethatcher and soil conditioner.
Hancock Seed has Bermuda grass seed available for putting greens, and the bags are available in sizes from one to 50 pounds. Some of the brands available from Hancock Seed include Postcard, LaPaloma, LaPrima, Princess and Riviera. The company also sells accessories for caring for the seed including fertilizers, pesticides, sprayers and equipment.