I bought grommets at an electronics store and they work just great! These are what you would use where a wire passes through a metal cabinet, that sort of thing.
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1971 Paramount P-13 Chrome
1973 Paramount P-15 Opaque Blue
1974 Raleigh Professional Blue Mink
1991 Waterford Paramount
Holland Titanium Dura Ace Group
Holland Titanium Ultegra Triple Group