Mommc realizing this may be out of the area of being retired but why not make your own yogurt. There is plenty of info out there on how to do it. Supposed to be fairly easy to do in a thermose. I read an article in a yacht magazine of how a family that lives aboard does it and uses it as replacement for sour creme when ever they are when they cant get it.
John
http://www.leeners.com/yogurtrecipes.html