I came across this amazing website that houses over 85,000 vintage sewing patterns. I was afraid to log on in fear that it would be a jumbled mess with an ugly interface like Reddit (my personal opinion). I was pleasantly surprised in the ease and look of the site.
It is sorted by garment type and when you click on one, such as dresses, it takes you to a page that has sub-categories to help narrow down your search. Once you are in the sub-category of interest, you can select on any of the patterns. If there is one for sale, there will be a link to the seller. Of the five I checked, four of them had a link to a website for purchase. You can also do a google search with the pattern name and number to see what that yields.
This is an amazing resource and with this Spring like weather here in San Francisco, I have caught the sewing bug. Now I just need to get that dress form I've been searching for! Happy Sewing!