ASUS P4T533 memory question

I plan to buy this board (i850E chipset) soon. According to ASUS' website, they say to buy the Samsung RIMM 4200 for memory and that other memory made by other manufacturers may not be suitable for this board. I have no problems playing it safe and making sure to buy the Samsung brand, except for the fact that I can't find anyone selling it. I am interested in the PC1066 RDRAM and I'd like to preferable find it in a 512MB stick and use the continuity madule in the other slot on the board so that I can always add another 512MB later on. No vendor I've seen seems to have this. and I've only been able to find one vendor (newegg.com) that has the 256MB version. I'm sure someone on here must have built a PC based on this motherboard. Can you please shed some light on where I can find a 512MB Samsung PC1066 RIMM4200 module? I'm also hoping for a recommendation on a reliable vendor. Thanks.