Not sure which folder you have, but I've not had much of a problem adding stuff to my folder....I use a small fabric bag that collapses when empty so it just squishes when the frame folds. The water bottle cage and pump don't get in the way either. I use a light that mounts on the rear fork where there is no folding interference. The front light is clipped to the bag. Lots of brands would work. I am using a Cateye 7 Velo speedometer which also works pretty well and does not interfere with folding