So I already have some young bonsai that I got from the nursery, but I want to give my collection some authenticity. Where would I find bonsai seeds, not cuttings, seeds?

There are no such thing as bonsai seeds. Choose your species to grow and buy normal seeds, so much cheaper than from scammers selling bonsai seeds. Not only cheaper, higher quality and better germination rates.

Oh, I could have fallen into that trap thanks.