Watch out for speakers, saying "selling nos$ 1:XX". Contact them and give them the amount of gold needed for the revival stone and they will then get it from the mall for you.
The current rate on the US-server is somewhere around 1:20 (it increased just recently), the one on UK I don't know.
edit: If you are impatient, you can also speaker yourself that you are buying nos$ for a given rate. You might, however, need more than one speaker until you find someone selling to you.