I hear great things about this company:

http://www.bgprod.com/

They have an over the shelf product called BG 44K.

Here it is from their homepage:
http://www.bgprod.com/bgprofessional/bgproducts/autofuel.html

An idea on price:
http://www.autobahnpower.com/products.asp?recnumber=92
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1989 300CE Astralsilber/Schwarz
1992 300CE Schwarz/Schwarz