Walthers has safety tread for large scale the tread is about the same size as the tread on aristo gp-40's and sd-45's.
5-3/4 x 3-1/2" 14.3 x 8.7cm
Walthers Part # 643-501, G scale, $6.99, currently in stock at Walthers
Super thin polypropylene realistic raised tread. Easy to trim, paint and glue to any engine or model. Each package comes with two 3-1/2 x 5-3/4" sheets.