Cool! Now somebody else can take the ribbing for trying to restore an old Sunbeam.
I think you can find at least some replacement parts, but remember that even the OEM ones aren’t very high quality. I remember when those glass window grills were popular and Sunbeam was a major player in home grills. So that find is definitely a trip down memory lane.
One suggestion I have is to use the ceramic flat pieces with holes like I did on my crazy Sunbeam “The Judge” as seen in my thread that Bruce kindly reposted above. They will do much better than lava rocks and I think than even the ceramic pyramids.