I just went to Bourbon and Branch for a friend's birthday this past week. It wasn't just a 20s flapper party but a Great Gastby inspired party. I rented a costume from Costumes on Haight http://costumesonhaight.com/ . It came with a dress and hat for about $20 (2 day-1 night rental).
I also rented pants and a hat for my husband. I had bought him suspenders and some fun glasses but the he is so tall that the suspenders just pulled the pants up into Urkel-ville, and I still have no idea how the glasses are supposed to stay on one's nose ....
|even with a fairly sizable nose, these did not stay on my husband's face|
I also looked up Great Gatsby makeup and found this great YouTube tutorial. Great Gatsy makeup You can't see my eye makeup in the picture below (we started getting artsy with the pics), but 20s makeup really emphasized a downward slope of the makeup to make "sad puppy dog eyes" and lips in the shape of a bow. This can be done with a sharp lip liner and concealer.
Anyway, I had a blast and will always take any excuse to dress up and put on fun makeup. More fun to be had in the future!