Southern Railway Wooden Trestle Plans

Allen Cain

Does anyone have drawings of the wooden trestles that the Southern constructed in the 1950s (and earlier) to go across low marshes and swamp areas?  These were typically not very tall.  I would like to scratchbuild a couple.
Or, is there a good HO stand-in kit available?
Allen Cain
Modeling The Southern RR in 1955 in HO Scale