I have had annoying and driveway staining oil leakage from front of car on and off now since I've owned my 82 240D......

It appeared to be coming from the oil pan plug more times than not....I have just swapped out old oil pan for new one with new plug.....nevertheless, is there something I should be doing after oil changes to insure that there is NO leakage from the pan plug?

I'm told that there are copper washers that should be placed onto plug after each and every oil change to eliminate leaks from this source....I am unable to locate these washers online after several searches.....

Does this sound draconian or is there a source for these washers/rings or another item that will do the trick? Thanks.