Kevin, thanks for the reply and good luck in your hunt for an appropriate bridge--I have no suggestions on that score.
Plastruct offers a 30" single track truss bridge kit which you might be able to install two side-by-side:
KIT-2_c012c004-a2f2-4c3f-9ffc-3cd33f082fbe_1024x1024@2x.jpg?v=1566432947" />
https://plastruct.com/products/3002-kit-3002
NOTE: The gibberish above the link is the result of pasting a photo of the bridge taken from Plastruct's website which appeared fine before publishing my reply.