That's a tough one. Some designers offer petite sizes but not all. From what I've found, you have to try on large sizes and either custom order your size in petite, or fix it in alterations if their smallest size still isn't small enough. I couldn't find any designers that catered to petites. I've heard Vera Wang does but that blows reasonably priced out of the water.
Are you a size 0-1 in your everyday attire? If so, then you're most likely a size 2 in bridal dresses since most bridal gown designers use European sizes. So if you're typically a size 0, then your wedding dress size is a 2; if you're normally a size 2, then your wedding dress size is a 4 and so on. I'm also petite and it was so hard finding a dress and trying to figure out whether or not it was something I wanted because the sample sizes were usually way too big (e.g., size 8/10). I have read lots of posts where many brides have purchased dresses online, off of Amazon, bridal marts, E-bay, but most of these dress sizes are sample sizes, so I see where you're having problems. Have you tried Craig's List? Usually, you can find plenty of wedding dresses there. And the upside of it all is that you can find someone in your area who's actually selling the dress. Also, what is your definition of cheap or reasonably priced. Depending on your dress budget, a local bridal salon can also be a sure bet.