I am looking for a poster of a very attractive women wearing a black
pinstripe power suit, with hornrimmed glasses and her hair tightly
pulled back. It is for a friend's 21st birthday; the bigger the poster
the better. Where can I find/order it?

I don't think you'll find a ready-made poster of this, I checked at
allposters.com with no luck. Then I went to www.gettyone.com and did a
search in creative, royalty-free images using the keywords - business,
woman, glasses. There I got more than 300 images to go through, some
of which were close to your description. What you would then do is
purchase the largest file in your budget, contact a local output shop
that makes large images for graphic design companies and see what
format they can take for output. Convert the jpeg into this format
(eps or tiff, probably) and burn onto a CD. You might also be able to
take the file to a local fotomat that deals with digital files.