I am in the process of printing this. It is a big job but should be worth the effort.
www.thingiverse.com
Found it on this site by googling "G scale trains"
First pages have some interesting items
www.stlfinder.com
G Scale Pedestrian Bridge. by TrainmanBruce
This Pedestrian Bridge is designed for G Scale. It might be possible to scale it down for O scale, but small Balustrades etc are 2mm in G scale. There are 20 STL files. Some need multiple prints. Details are below. I assembled my model without glue, but pieces can be glued if desired. No...
www.thingiverse.com
First pages have some interesting items
g scale
l➤ g scale 3d models ✅. I made this for a stormwater educational diorama. ... Printed well in G scale; could easily be scaled up or down as necessary though. ... Have fun!
www.stlfinder.com