Here is a Replacement for the " I1" (i1) Runner on the MG Buster Gundam. (The forearm Armor piece)
Mine came broken in the bag, but it's a symetrical piece, so I 3D modeled a replacement part.
You might need some superglue to get it to stay on there, but it should be to scale to fit okay.
Artstation.com/nateordie to see production video / photos of the Gunpla model. Hopefully this helps if anyone else needs this part.