Several people responded to your first inquiry about a month ago:
proto 2000 2-10-2 side rod screw - Model Railroader Magazine - Model Railroading, Model Trains, Reviews, Track Plans, and Forums
Help! Having diffuculty finding a replacement screw for the driver connecting rod on my 2-10-2. Last year I swapped out the center driver for the traction tire set that came with it. I should have used loc-tite. It backed out and is gone. Seached google, e-bay, walthers. I cant determine the screw size or pitch. Does anyone know where to find one. Any help woul be appriciated.