you just going to have to shop around online. search for the wavemaster bags. those are the free standing ones. tons of different sites sell them, and their prices range from site to site. but there are some good deals out there, ive seen some advertised for only $80 or so before. shop around and order it from a site you trust.
theres also equipment you can buy that will enable you to have a hanging bag even though you dont have a place to hang it.
start here >
www.google.com
type in wavemaster bag