I have it on good authority that the fuel pump relays that were used in 560SEL & 560SEC models, are no longer available from MBUSA.
The part number for these relays is 003 545 25 05.
There are aftermarket versions available, but these are not nearly as reliable as the factory units were. Example of aftermarket parts: http://www.autohausaz.com/search/pro...ber=0035452505
It is HIGHLY advisable to get used factory units from the wrecking yards.
The 1986-1989 US models originally used a different fuel pump relay part number, which was 003 545 01 05. This part was superseded to the above part for the 1990 and 1991 models, 003 545 25 05, some time back.