I have scoured the Internet, but I can't find any evidence of a toy called "Harry Potter Concoction".
I have a vivid memory of a commercial that had a song with a low, deep voice and the lyrics:
Make a concoction...A Harry Potter concoction
If I remember correctly, it was similar to Creepy Crawlers
I am trying to determine if this was some sort of crazy dream or if it really existed.