Not a replacement, but I do remember some enterprising individual offering a plastic or resin extension to the folding pedal, to give a bit more foot room. Size is my only criticism of it but I do have big feet.
I find Brompton pedals to be OK but I always wish for something better and probably grippier too. Does anyone have experience with upgrading pedals on Brompton? There are some models with quick release, but then where to store removed pedal. Any good upgrades with foldable design?