I have some Datura which might interest you. I recently came upon some seeds from a double yellow, which I would be glad to trade, but I don't know what kind of white you want. I have some Datura inoxia, which is quite fragrant during the night, especially right when the flower opens for the first time. Take a look:
http://i53.photobucket.com/albums/g79/Tall_Mike_Bismuth/Daturabloom.jpg

http://i53.photobucket.com/albums/g79/Tall_Mike_Bismuth/open_close.jpg

http://i53.photobucket.com/albums/g79/Tall_Mike_Bismuth/daturaonmorninghillside.jpg

http://i53.photobucket.com/albums/g79/Tall_Mike_Bismuth/Datura.jpg

http://i53.photobucket.com/albums/g79/Tall_Mike_Bismuth/MidnightDatura.jpg

Once again, I don't know if you're looking for Datura inoxia. There is a single white variety of Datura metel called Belle Blanche, but I don't have that. People have been asking about my Datura wrightii lately. You might be interested in that. It has the largest flower diameter of the Datura genus, with a blue to violet coloration along the flower's edge. It''s easily the most fragrant Datura I have. I'll get some pictures of that when the new flowers open, which should be in a day or two.

That covers me. Unfortunately, I can't find anything that interests me on your exchange list. Where do you live? You might have some Datura species growing along your roadside in your state that suits my curiosities.