So managed to fit a city ac filter. It was only a bit bigger at the end, but it was easily adjusted.
Using a cutter, cut the bottom and sides only. Credit to the person who did this on youtube for another model honda overseas.
Make sure the filter air flow direction is facing the right way, airflow is top to bottom
The end of the filter sticks out a little bit, it can be easily bent inwards. Close the flap. Holds in place pretty good.
Top overview before and after filter.
Edit: Come to think of it, if you can get the proper front cover for it sold overseas, the filter should fit perfectly. The temporary flap is meant to be disposed off.