Mine works fine with a DSE clone stick, about 2/3th the price of a sony one. (only available in AU, but they will post). I'm sure you will be able to get cheaper ones locally.
As an employee of Sony, I can confirm that ANY MS will work with your camera, despite things that some retailers or websites may say. The only thing you need to watch out for is sticks above 64 & 128Mb for older Sony products (ie before 2001) and for using MS in Magic Gate only products. This should not affect you on a newish cybershot DSC. Good luck!