[FullRangeMan]

Not if the Internet is your friend! Google "Cork block" and see how many options there are. This Amazon listing is one of quite a few sites selling cork blocks.  http://www.amazon.com/Hugger-Mugger-Cork-Yoga-Block/dp/B000C9KZ18

Thanks Bender; these bamboo blocks are great, may be better than cork:
http://www.amazon.com/Hugger-Mugger-Bamboo-Yoga-Block/dp/B000LGMLSW/ref=pd_sim_200_2?ie=UTF8&dpID=41Po4lHlJuL&dpSrc=sims&preST=_AC_UL160_SR160%2C160_&refRID=14SF3TXKBZRGNZGD6YC1