Perhaps you could contact the University of New Hampshire, where he worked.

The attached article states that he introduced more than 60 varieties of various plants.

Here is a link that might be useful: Honoring Elwyn Meader

I had the honor of meeting Mr. Meader, in 1995 I think.
He showed me around his place. It was a memorable experience. I tasted my first ever persimmon(the Meader). The miniature peach bushes/tree(s) were amazing. A very nice fellow!

Douglas

"The Many" cultivars is a good way to put it. I think SSE published an interview with him years ago, and the list was impressive. I'm pretty sure he developed that fall blooming red raspberry everyone grows.