From your description replacement would be the best route since the bumper that fell off is extremely corroded. There are members on this site that are having cars parted in the
Mercedes classifieds swap parts forum.

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'96 C220 138,000mi, '95 E300D 239,000 mi., '87 300TD 214,000mi '88 6.2 Turbo Diesel Chevy Conversion Van 253,000 mi.