RM-Z 450 FMF Headers problem

I have a 2005 RM-Z 450 with a full system FMF exhaust with Megabomb titanium Headers. Recently i found a crack in the header and I removed it to fix the crack. Upon removing the headers, there’s a steel insert that connects to the cylinder head. To keep the gap between the head and cylinder head closed. I lost the steel insert in between the process. & now I can’t find a replacement nor the actual name for the part. Would anyone know the name of this part or give me any information about this part? Please help!