Where do you buy them ... locally or online?
I've been buying mine at True Leaf Market for a few years. When I first got into salad gardening*, I found they were one of the least expensive sources (it was Handy Pantry then, now acquired by True Leaf Market). Germination has been reliable.

* salad gardening: https://www.amazon.com/Year-Round-In...9913604&sr=8-5

Salad gardening is sprouts grown in soil, versus sprouts grown just in a jar. The book I linked outlines the method and gives lots of tips. This will be the 5th winter for me in growing soil sprouts. I don't tend to use these as a salad on their own(although you can, and I have) but as an addition to purchased lettuce or for sandwiches.