225 slant 6, exhaust manifold triangles

Hi guys, I'm new here, very glad to have found this site. I have my grandparents 69 GT. it's pretty much stock. I'm taking the head off for a rebuild and noticed a couple of the triangular washers were MIA. I have done a lot of searching, but have been unsuccessful in finding some reasonably priced replacements. Can anyone point me in the right direction? Many thanks!