I do believe the engine panel is the same for all W124's. same as the transmission belly pan. Sans the cabrio's since they did not come with one due to the extra chasis bracing.

They are hard to find in the yards because they are either

1) lost from previous owner
2) ripped off from when its in the yard
3) supposedly thrown out but are actually in someones garage, but thats usually w126 specific -chortle-

call your trusty parts person. I think they are not that expensive