From the "Why didn't I think of that?" file --

Just because a manufacturer does not make a product for your particular needs, does not mean you do without. Consider the following:

Use our Sn3 HERMOSA CREEK BRIDGE for your HO Standard Gauge needs. The width through the deck is just right for HO. The larger size is in proportion to the heavier equipment in HO. And the length is about 65 scale feet for HO.

The same reasoning can be applied to S-Scale Standard Gauge. Use the On3 version. ;-)