While high heels are not for everyone, low heels (1-2 inches) are perfectly pregnancy-friendly. They are much more stable and healthy than other shoes. Make sure you find a pair with preferably wide-based, sturdy heels, soft and comfortable soles.
Go shopping in the evening, when you feet are most swollen due to the fluid retention. Otherwise, you risk buying a pair that will only fit you until early in the afternoon. Reduce the time spent in heels to 2-3 hours a day, and do some feet exercises after you take heels off.