It depends on the type of calipers on the car, the original calipers were made by Girling. these are harder to find and not likely available through your local auto parts store. Many 230sl have had the calipers relpaced with ATE calipers from the later 250 and 289sl these calipers were widely used on Mercedes sedan models and pads for these can often be found at chain parts houses like a NAPA store, the pads available from these retailers are usually not of very good quality though.
Before you buy anything look for the brand marking on the calipers.
