there are several adapters out there. some are purpose built to accept rca and s-video adapters and feed them in to vga output. Or you can buy a vga--rca cable and find female-female plugs to interconnect with the ps2's standard connector. Or you can flat out buy the vga-ps2 connectors that are out there.
Now that I answered the question, i recomment
since all you have to type is Playstation 2 VGA to get enough responses to keep you occupied for a while.