ORIGINAL: Avaiojet
Your local HDWE store will have a large selection of these washers. You could buy thin brass sheets and make your own.
Drill the hole first then cut the outline.
You could remove another to see what they are really made of.
I don't think it's paper?
Certainly there must be enough dead engines of that brand in boxes in modelers hobby areas. You might get lucky and your Thread my get seen by one.
Hope this helps.
Thanks for your answer. I have the broken one in my hand I think it might be teflon or nylon. It's white and very thin. And you're right, it's not paper. The size of the Teflon washer is about 8mm in the outer diameter- and 4mm in the inner diameter. And like I said, it's very thin. So thin it's about regular paper thickness. I'm not sure what its for, I'm guessing it acts like a bearing between the camshaft arm and the inner side of the head.
Pete