If you have good command over commerce then better to opt it. You may have a look at past papers and syllabus before reaching the final decision. If no single book covering the syllabus is available in the market, it doesn't mean that the subject can't be opted. No single book for science/Business/Accounting/technical subjects like Psychology, Computer Science, Physics, Maths, Chemistry, Business Administration, Accounting, Zoology, Botany etc is available for competitive exams but even then aspirants prepare these from different sources and get very good scores.

__________________
Best end of life is not knowledge but action.
Don't limit yourself to what you think people are expecting!