EmbroiderThis.com has some very nice ones.

I buy a lot from Tuesday morning. good luck!

Got to Google and type in napkin blanks. There are a lot of places out there to get them. I too have picked up many at Tuesday morning, but it is hit and miss what is there. Too, Sams club, has the packages of napkins like the restaurants use, and in 3 or 4 colors, I think. I have not purchased them but have looked at them from time to time - especially since I usually need 15-18 at Christmas dinner.

www.allaboutblanks.com usually has a good variety of table linens.