I am looking for shops where I can take my mother to purchase a dress
for my sister's upcoming wedding.

Specifically upscale shops with a good selection of plus sizes and
great service. Money is not an issue. Simply looking for the perfect
dress for a fabulous person.

I live in Sonoma County and therefore I am looking for shops in Napa,
Marin, Sonoma, and San Francisco counties.

Hello cdavis-ga:

Thanks for your question as it was a pleasure to do the research.
While I was doing my research on your question I came across many
bridal links in the bay area but I chose only the best link that will
serve you as a guide.

The best guide to bridal and bridal maid dresses in the Bay area is:

http://www.weddingweb.com/sf/sf.clothing.html

The link provides addresses of 30 shops that will meet your needs. The
list also provide additional information such as custom made or non
custom, price range, type of cash accepted and timings.

Other Useful Links

http://www.thecityofsanfrancisco.org/bridal/ 
(You may ignore the first listing as it is an advertisement)

It is a directory of 31 shops in SF area that cater to wedding related
dresses.

http://www.weddinglinks.com/countymap.htm

Click on the California map and than select
‘Gowns-bridal-formal-seamstress’ from the category to find bridal
shops anywhere in CA.

ANOTHER SHORT LIST 
http://www.usbridalguide.com/local/ca/san_francisco/bridal/

Again, I could have provided the listings from more pages but I
believe that quality is more important than quantity.

Please clarify if you are not satisfied. Good luck with your search.

I also want to pay my best wishes to whoever wedding it is.

Regards,
Leader-ga.