Baueda has their 15mm M2 Modular Pontoon Bridge available for purchase on their online store.
From their website:
The M2 Treadway Bridge was a heavy pontoon bridge that had up to a 40-ton capacity. It could be deployed in almost any lenght and it was used over major rivers like the Rhine and Moselle. The bridge was assembled from several purpose-built components including the U.S. M2 pneumatic pontoon, M2 treadway bridge sections and access ramps. It would take five and a half hours to an experienced crew to place a 362 foot section of M2 bridge in daylight and two hours more at night. Two pontoons fastened together could (and were!) used as farries. This model is a very accurate scale reproduction and has plenty of beautifully sculpted surface detail to help you in painting!
Like all other models in this range it is made of tough POLYURETHANE; it require no assembly but can be obviously glued in place if you like. Overall bridge size is approximately 180x95mm and the height is 18mm. You can confortably fit a standard infantry Flames of War base on a single pontoon.