CM Wasson sells these, for Bromptons, but not sold by them.
so a 3rd party contract sewing project.

http://www.foldabikes.com/PriceListH...viro_tote.html
looks generously sized.
But you will have to measure your size requirements, of the folded bike
for width, height and length.

Bromptons are about 4 cubic feet , folded , 12x24x24.