I am covering the belly of a Model III.

I am looking for a way to access the small nuts associated with the control stick mechanism hold down through the floor. The manual suggests using the large inspection hole rings (as used on the wings). I am hoping for something much smaller (just enough to see through and get a deep socket in). Maybe 1/2" to 3/4" ID. Does anything like this exist out there? Maybe an aluminum or nylon washer with a 1/2" t0 3/4" ID with a good fitting plug of some sort?

Any thoughts ot ideas that others have used for this?

Larry S.