How can we find more flowers in the delicate bouquet collection if the quest's already done.

I've finished the quest the delicate bouquet, and charged a golden flower already. However, i want to have some flowers in the collection more - Lilly, Gebera, Orchid.., but cannot find anywhere else even from a succubus.

Apart from buying them, how can i do?

buying them is the only way I know of.

If you want to use this artifact, then I'd save your money and just use turtles, they are far better than the golden calla.