The product i use for a sanding sealer is a high gloss spray lacquer by Deft.
Here are some photos of the finished product. It's not a one piece... but it sure does look like one.
https://photos.app.goo.gl/iHvDUTmRT4opq7SD7
Nice Kirk
Is that phenolic for the flat head bolt and how thick does it need to be to get a full contact for the flat head countersink bolt?
G-10 Garolite.... you really only need about 1/8" thick, but i like to use 1/4" stock, counter sink the bolts a bit, then sand the overlays to match the top of the bow bolts just right. this finished out about 3/16" on this one.
i always sand , paint, and clear coat these bow bolts to match the matt finish. keeps them from rusting and it looks cool. Kirk