I've had colleagues with engineering/law background, but on top of their basic degrees, they are equipped with either the CFA or an MBA from a top tier uni (think INSEAD, Oxbridge, HKUST or the Ivy Leagues).

If doing the CFA or MBA isn't that feasible at this point in time, perhaps you should try out the Bloomberg Assessment Test or CMSRL exams. Having these done, would perhaps demonstrate the minimum amount of technical knowledge that is expected of a IBanker.