Where can I find pretty, non-diamond engagement rings for under $250?

Getting engaged soon, but we don't want to spend thousands on a piece of jewelry, and for ethical reasons, we don't want diamonds. Looking for a solitaire stone (can be a diamond simulant) preferably set in a thinner pave band. Any ideas as to websites or stores I might check out for something nice? Something reasonable, but not cheap and tacky looking. We want something unique but with the ability to be timeless. Thanks for your ideas!