Accounting & Commerce

Let's look at the few fields to see what kind of jobs you can find to satisfy the requirements.
Front office: Actual Trading or Trading Desk support, where you help the traders make their decisions.
Middle office: Operations in big investment banks, they deal will processing of the trades after it's done, they enrich the trade and record it in Accounting Systems.
Back office: All kind of Reporting, Analytics, Risk calculations, Regulatory etc.
Research: Fundamental, Technical Research, Top to Bottom (at Country / Macro level, narrowing down to Company level) or Bottom to Top (Compare few companies and see why they are earning more than peers or if the peer group is doing better than the industry as a whole), Industry life-cycle phase or Product life-cycle phase etc. These groups do all the calculations that enable the Front-office to make the decisions.
Tech: Coding applications that enable any or all of the above
Supervising: Directly managing / supervising the team that's doing any of the above.
Teaching: If you are teaching CFA candidates
All you need to prove is that either you made portfolio management decisions or your work helped somebody else make those. Also this doesn't need to be continuous 48 months, it can be different positions with different companies over your entire career. You can also include the internship / positions that you have had while preparing for the exams.