In fact, it is available right here (click "Buy Parts" above) or this link.

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2BG122QHI2BG122XS1&year=1989&make=MB&model=260-E-001&category=All&part=Throttle+Microswitch

$27.00 and your troubles should be over.

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2008 E350 4matic / Black/Anthracite

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Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black