Can anyone suggest where I can look for a 1GB or 500MB RAM module (DS3333?) for my brother’s Thinkpad X31? Please let me know how much these cost, too, if you know 
Try the shop on BaDe in ChuangHua Computer Market area that is a Taiwan brand name memory company. It is the last or next to the last shop of the row on the north side of the street closest to the intersection where the bridge use to be before it got tore down. Of course this would be the West side of where the bridge once stood. I am sure they sell it there. They sell Memory for everything from notebooks to printers, they make it all. It will definitely be MUCH cheaper than buying in the USA. Don’t worry if it is not IBM brand name, or something like that.
Crucial has memory modules for most computers, but not sure if they ship to Taiwan www.crucial.com and they’re guaranteed to work.