What you have pictured there is only the outside of a scupper assembly. It's the flapper part. Meaning, it's a separate part from the thru-hull piece and can be used by itself or along with a thru-hull (with or without a hose). It simply installs OVER the thru-hull part. Personally I've never seen a flapper assembly made from SS. However, there are thru-hulls with an internal flapper (an all in one assembly) and some of those are made from SS. Attwood is one of those that makes them. There are styles made with barbed ends to accept hose and also panel-mount styles which may work for you. However, you may need to enlarge the current hole that goes through the transom. The panel mount can either be cut down if it extends too far, or you could epoxy it in place - but the latter could create an issue down the road if you have to replace it.
My suggestions...
-- Stick with the original, white, PVC flapper assembly.
-- Go with a panel mount, SS scupper/flapper assembly that goes completely through the transom. Enlarge the hole, if needed, epoxy coat the interior of the hole for protection from water. You will see the nut on the inside of the transom. Go to Attwood's site and look at these.
-- Find a machinist that can turn a chunk of SS into the exact copy of that white, PVC piece
-- Last, but not least, hope that someone else responds with info about a readily available SS piece.
