The Lexar site has 512 MB smart media cards available( and I'm sure you can find other manufacturers), what sort of camera are you using?
My Kodak DX4900, set to take 4 MP pictures, will take 103 with a 256 MB smart card, so depending on the resolution your camera is capable of using and what resolution pictures you want , a 512 MB card taking 2 MP shots could hold about 300 or more pictures.
With just a couple 512 MB cards you could overwhelm yourself with pictures... unless you plan on taking more than 600 pictures, wouldn't two 512 MB smart cards be all you should need?
Buy.com
http://www.buy.com/retail/computers/....asp?loc=15579 has a Viking 1GB smart card for $242.99 after MIR and several 512 GB cards for around $95... it just depends on how much money you want to spend.
There may be other sites with even lower prices, so look around.