Found a good site to buy dairy cultures

I like making homemade sour cream, but I can no longer have a convenient local source for buttermilk with live cultures.

http://www.cheesemaking.com/shop/sour-cream-ds-culture-5-pack.html

Their packets are also available on Amazon, so if you have Amazon prime you can save a little on shipping.

I just got through making a batch of sour cream, and it has a quite nice texture and flavor after culturing for about 18 hours. I'm going to add a tablespoon of the sour cream to a cup of milk warmed to 86F and see if I can use the same batch to make some buttermilk.