Donnaricco.com is a great place to find dresses for any season, they have new summer and fall dresses daily. They do have petite sizes as well as regular sizes, and you can even search dresses by occasion as well!
Below is the link to one of the sites with prom dresses in size petite.
from topshop&dorothy perkins websites
I would recommend DressPro. They have a great selection of affordable dresses in many petite sizes. http://www.dressespro.com/petite-dresses-c-1_100.html
Petite formal dresses are gowns for a formal event like a prom or wedding, that are made to fit women of a petite stature. Petite sizes are women's 0-3.
A lot of stores in California carry petite formal dresses. Major retailers like JC Penney and Macy's have entire petite sections.
David's Bridal is an excellent selection for bridesmaids dresses. They have several options for sizes including plus size and petite. Empire style dresses work good for both plus size and petite.
The only major difference between petite formal dresses and regular formal dresses is that petite formal dresses are made to cater to women who are short in stature. So, certain elements of the dress, such as the skirt/train or the straps, may be constructed shorter in order to accommodate the smaller frame of a petite woman. Besides that, petite formal dresses are often identical to regular formal dresses in terms of styling, cut and adornments. When picking a petite formal dress, it is best to choose a dress that works to lengthen your torso. Gowns that are one color are good choices, as are gowns that don't have too many layers. Petite women are advised to avoid dresses that have large or horizontal patterns, drop-waist syles, dresses with too many gathers and dresses with belts.
Ann Taylor does sell petite women's clothing. You will find blouses and tops, sweaters, dresses, suits, pants and shorts, and even skirts, all in petite sizes.
David's Bridal
Women's clothing has always been the main business category of the FashionTIY online wholesale market. A variety of styles to choose from. Online reservations can be completed through the official website or app.
The difference in sizing between regular and petite dresses is the length. Petite clothes are made for shorter women so the length at the bottom of the dress and on the sleeves would be shorter.
As long as it's in the summer or the spring you can find plus size dresses on the website. They offer a wide range of plus size dresses and petite sizes as well.