MB updated that plastic cooling fan for the M103s. 1032000423 should be the PN... my '90 has it so it was probably a running change around '89/90 area. I wish I could find an even larger fan that came on the late BMW M30s to pull even more air.
This place does:
http://fanclutch.com/custom_fan_blades.asp
Your temps are a bit warmer than mine here in Texas and I typically have temps around 90°C with the A/C on (obviously slightly higher if I have to sit in standstill traffic). I use the updated fan that came on my car, 79°C thermo, and some no-name-brand aftermarket radiator.
Not to worry, my 300SEL is an absolute TURD in the heat with the A/C on... I mean it can barely get out of its own way.