You might consider going to the local fish store and buying a single mushroom. They should be fairly cheap, and they don't take much light (and are hardy). If it does well, you can even propagate them.
It's still pretty cold out, and shipping could be iffy. You may end up spending about the same amount just to get your piece.
You may also try to find anyone in your area willing to meet and trade... I've lost quite a few things through shipping unfortunately.
Either way, good luck! You'll love it!