Hi!
You can't go for a science/ technical postgraduate course in India without having science at the graduation level and you don't want to repeat your graduation. The only solution to me seems to be to go for an MBA and specialise in IT/ Systems.
Please note that you will have to make a lot of effort on your own to make sure you are tech-savvy before you start with the hardcore IT/ Systems electives in the second year. Therafter, only your own sound technical knowledge is going to convince the interview panel during placements. I do know of people coming from commerce background who have succeeded in the technology field this way.
All the best!