Go to Stormsong Valley and transmute Barberry Shrubs into Shrubbery Bubbles and gather $1oa of them.
Bring them back to Elric and observe as he tries to use them to make the stone.
The stone this recipe becomes is a transmutation stone. What if the missing reagents to make it come from something that's gone through the transmutation process?
I'm willing to try anything at this point. Here's an old recipe my ex-partner devised.
He used to go out to Stormsong Valley, just south of the Highland Flats and change the shrubs there into bubbles.
Bring back some of those bubbles and we'll see if they're what we've been missing.