Lead sheet & foil is still reasonably available in certain industries. Old school roofers often have some sheet around. If you know anyone in the X-ray or better yet the nuclear medicine / nuclear pharmacy fields they'll have all kinds of it.
Thin Pb sheet is really easy to work with -- can be cut with a utility knife. I think a reasonable washer could be fabricated out of an appropriate thickness of sheet by cutting the OD with scissors or a utility knife and using a cork borer or an office hole punch for the inside hole.
Pete P.
Harborcreek, Penna.
