Unfortunately the spanner is under the bunk on the boat in Mexico and I am in Ireland.
It couldn't be more simple. I took an A4 piece of paper, measured the width and depth of the nylon nut with my vernier, drew that on the page, then sketched the shape of a spanner/wrench around it and had it cut out in machine shop.
So you have a very thin wrench/spanner, with wide jaws that slides under the quadrant, the nut usually takes a quarter turn every 12 to 18 months.
On a separate point, I also got the same machine shop in Brazil, to make me a pipe which slides over the drive shaft. The pipe has a round flange that moves along the pipe, you can fix it in the exact position required with two allen screws to push in the oil seals for the wear bearing, by putting a couple of washers over the drive shaft and tightening up the long Autoprop nut by hand.
I appreciate photographs would be better, I just hope the above makes sense to you.