I found this excellent card holder that was in three pieces. I cut up the middle piece and added it to the side piece, hence, you only have to print this one model.

This insert allow you utilize all available space in the original boxes. It fit two rows in the smaller box (featured) and three rows in the large boxes.
There is also storage for tokens and bits, with rounded bottom for easy pickings.

All credit go to Jarcec who created the original model.