Glad you've got Smoke Silver - a nice, slightly retro, classic colour. My Dad had a 190 in that shade years ago, I'd know it anywhere
So about the bumpers: I ordered the front from Ebay and the rear from MB as the estate needed a different part. Ebay probably has saloon versions of the rear for yours (search W124 bumper strip) but they often seem to be the later painted variety that come in primer.
Euro car parts or GSF may also stock them. Remember to search for 1986 - 1993 model years for the black ones.
This is the front one I bought from ebay (no problems fitting it, it was fine)
MERCEDES E CLASS W124 1984>1995 Front Bumper Moulding Strip Black | eBay
The OEM estate rear version from MB was £80 or so. Not noticeably different in quality - maybe a slightly different grain on the moulding.
The foam inserts are important as they obviously absorb impacts and prevent the bumper strip cracking. Mine were broken or missing completely (in the front) but they are still available from MB and not expensive. Phone a dealership with your VIN and they will be able to order them if you need them.
Part number, rear strip (black/unpainted) for saloon:
124 885 0321
Part number, rear strip (black/unpainted) for all models is:
124 885 1021
My car is a dark colour so the strips don't really look much different from the painted ones it came with originally, but even on a pale colour like yours they look fine (like the on older models). Better to have nice new black strips than cracked, filled or touched-up painted ones, anyway.
Let me know how you get on with it. I have a diagram for bumper removal I could post - don't need to lift the car to do it, and it's just a few bolts to get them off. (You do have to to remove the whole bumper to change the inserts as they are clipped in behind, but it isn't hard to do at all.)