Get a weight lifting belt from Wal-mart, Target or where ever its cheapest. get the velcro kind that is adjustable. That way you can use it for after you deliver for abdominal support too. Mine has suspenders and the side straps on the belt are easily adjustible because its all velcro. It is over 6 inches tall and has back supports or "boning" in the back. I pulled my stomach muscles while having morning sickness and every time I had morning sickness after that it just hurt worse till I got the support belt.
Regular pregnancy support belts are narrow and I haven't found one that helped.