Non-diastatic malt is a sweetner and flavoring agent is available in the supermarkets as barley malt syrup.
Diastatic Malt helps break down the starch in flour and is used in home brewing and baking. It helps break down the starch into sugars the yeast can feed on. Find a home brew supply store in your area and ask for malt powder. Most of these stores don't have a clue about diastatic and non-diastatic. The diastatic malt is used for home beer brewing. I buy either medium or dark malt powder. It also comes in light but I like more bang for the buck and the darker it is roasted -- the more flavor. BTW it is fairly cheap and if you have a local home brew shop. you'll save shipping costs