Just a long shot since I don't know the dimensions of the Buick radiator shell, but maybe you can adapt a stone guard for a '29 Ford. You could probably make your own screen out of something from a hardware store but chroming a screen looks like a lot of work to pre-polish it. The stainless steel screen from Speedway (Part No. 911-22151) is $120 and might be adaptable? Otherwise I have no idea where to get stainless steel screen. Maybe you can make your own outer edge from angle iron or bent flat stock and then cut the Model-A stainless screening to fit the Buick shape?

Don Shillady
Retired Scientist/teen rodder