I buy my vitamins at the health food store. They are pretty common however I've also found them online. You might want to order some through the web if you don't have a quality health food store nearby.
I take Nature's Plus Source of Life prenatal vitamins. All natural, whole food concentrates... kinda expensive, but they are really high quality. As for DHA, I'm taking flax seed supplements (although I've also taken Spectrum Essentials Fish Oil--But if you buy Fish Oil make sure you buy a brand that certifies that the mercury, lead and PCBs pollutants have been filtered out).
On a certain level, it may not matter which brand you specifically buy as long as it is high quality and, especially in the case of Fish Oil, certified as containing no pollutants.