You can probably find a good power supply at a thrift store for a couple bucks or use an old laptop power supply.

If you really want to avoid power supplies you could get http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=58315 but you'll need an xt60 connection as well (http://www.amazon.com/gp/product/B013W119X0).

Personally I would try to get a power supply.