In fact, colored contact lenses like blue, green, grey and black are very popular with many people who want to change their eye color. While white contact lenses are not so common that we can hardly see people wearing them. If you want to get white contact lenes, you can go to any optical store and ask whether they offer white contact lenses. If you can't find them there, you can go to other optical stores to have a look. Good luck!
If you can't find it in local optical shop and have no idea where to start. You can search it online such as Amazon.com or eBay.com. Besides, there are some specialty sites that sell eyeglasses and contact lenses. I have saw white contact lenses at colorlens4less.com and youknowit.com. And they are affordable. If you want it for fun, you can try the contact lenses online.