The hole does not have a raised rim. The depth of the plug would originally be the thickness of the body plus the thickness of the vulcanite covering. Hence the plug is proud when the covering is removed.
Since the camera has the collimation hole we can assume that it is quite early and of interest to those who collect these things. Having said that I don't know if re covering a camera impacts on value.
I don't think tape or paper is a long lasting solution. The covering will sag into the hole in time.
It shouldn't be too hard to find a disc of steel or alloy that is close to the right thickness and close to the right size. This could be epoxied into the hole, sanded flat and the camera recovered.