How do I tell my fiance that after 2yrs engaged I'd like A FAKE ring rather than him get my hopes up for....

Okay....... so. My fiance and I have been engaged for almost two years. We "decided" one night in bed when we thought that we had a limited window to have a baby. No romantic proposal+financial woes=NO RING! More than once he has taken me ring shopping and more than once at the end of the shopping trip came home empty handed. He's gone on his own and still... no ring. How do I tell him that I would rather have fake rocks and a romantic proposal than get married with no ring. Its almost embarring when people ask me about my nonexsistant ring. Please help. I don't want to sound aweful and greedy and vain but, I would really like a ring!