Talk to Jin H Kim, he'll send you stickers if you send him a postcard that shows something to do where you're from.

As far as I know he's still doing that.

If that doesn't work, check out:

http://www.rubikshop.com/cgi-bin/shop.c ... at=diykits

They have a lot of replacement stickers for sale.

I found this site a while ago. It get's pretty pricey, but they seem to have a lot of good vinyl.

http://www.signwarehouse.com

Arnoud, go to a banner or sign making shop. Businesses that specialize in making vinyl signs for store windows or graphics for cars will have exactly what you need. That is probably the quickest and cheapest way to get large amounts of vinyl sticker material.

Jin's suggestion is a good one as well. You can get far more colors than just the usual cube ones at a place that does car lettering. And if you ask for scraps, you can often get them cheap as well.

Definitely, go see if there is a sign shop nearby. They are incredibly helpful, and you can get great deals on scraps. Even if the scraps are what you could consider mint condition, just not big enough for their needs, you can get great deals. Plus, they can cut it for you extremely professionally.