--------one place for getting it is the website for MOSES.  Oil seed radishes are supposedly top notch for cover crops, etc. .........but, as I recall, the places where such will grow have to be of a certain type.  I haven't looked at using the radishes for several years, but, for example, at that time I vetoed them because either I didn't think such would do well in southern IA, or the cost was going to be too high.

Also........I checked with Usha Rao about the effect of neem on flies, etc on livestock..........if you want the memo she sent to me, then send me an email, and I will return a copy.  (My email addy is accurate.)