Attached is a file that has the recipe and a source for the ingredients to make your own alpha-alpha Dipyridyl.
I do make it myself and it is pretty simple but always be careful to limit your exposure when making it and when using it in the field.
The standard caution about using it as a positive test is to make sure that the soil surface you are testing is naturally moist and did not have contact with the shovel. The metal in the shovel is reduced iron and will give the red response. I am including the full recipe and my invoice from the last time I bought the ingredients. I also bought the magnetic mixing bar and table on ebay.