Lambswool seat-covers are not bad...... extremely comfortable and there's an ebay market for used ones if/when you find proper junkyard 116 blue leather instead.

The best lambswool designs include headrest covers and list for somewhere at/less than $300 a pair...... w123 seats require adaptation for seat rails to fit - and they never made leather 123 seats - with lots of 20 yr old 123's seats suffering similar problems as your SEL.