Universities offering PHD without masters degree

I am an Information Management and Systems student just about to graduate in three years from college. Due to financial constrains I would like to pursue a PHD degree directly without having to go through Master degree which is extremely costly. I am determined to get a PHD either way. I have a 3.7 GPA and I got 730 in GMAT. I am looking for a good university (top 50) who offers Phd programs in economics, eCommerce, or something that is economics or computer science related without having a master degree. Any suggestion will be highly appreciated.