I'm not an ant builder but I know many ants these days are 3D printed in plastic, usually Nylon or ABS, or built from sheet plastic bought online. Given you only have 150g its the go to choice as its cheap and light.
Ant builders will know better but if I recall, 1-2mm HDPE is quite common, and then 1mm Polycarbonate as well. Some parts are metal like discs and scoops but the majority of the bot is plastic.