I bought mine on Craigslist, and I sold it on Craigslist when I was done. Sometimes you see them in kid stuff consignment stores here, too. Another thought, since you're still a ways off from TTC, is to set aside a few dollars a month toward a Hypnobabies fund.
70% of the U.S. population now lives in a state where same-sex marriage is legal. At 36 and counting!
I attempted hypnobirthing with my last and it didn't work because of awful back labor that I never expected and could barely handle. I wonder at the difference between that and hypnobabies. I wish I had more time to prepare with one of the two as I think it would really help. I hope you can find a good deal on it.