Van Dijk lists the filters at $7,50 each. That includes the metal washers and the large skinny rubber ring. The other rubber rings (bottom 2 and top 1) are another $3 but these do not require replacing that often. The manufacturers that I am aware of, that are all OEM, are Hengst, Knecht and Mann. You have to be sure that the filters are the right type of course.
Cees Klumper in Amsterdam
'69 white 280 SL automatic