My cousin was 9 months prego as a bridesmaid, she bought a regular dress and then brought it to the place that was doing the sizings and they cut the dress and put in strechy material on the sides that matched the dress...so that could be an ideal, you couldnt even tell the altered the dress
You've probably already looked into in, but there is a David's Bridal in Dallas and they should carry maternity dresses. Otherwise, I am not familiar with anything in the area. There are a lot of internet sites, but it is always such a risk to purchase something so important over the internet. Good luck and I hope you find your dream dress.