Is your concern play between the rudder stock and the gudgeon bracket? If so, I had a similar problem but have overcome it by changing the M12 through-bolt to an M8 one, and fitting Delrin or UHMWPE bushes - one from the bottom and one from the top of each gudgeon. I turned the bushes to be a tight fit in the worn holes in the gudgeons, and tightish on the M8 bolts. The first set, installed about 3 years ago, have now worn a bit on the bottom gudgeon, so I am replacing those this winter. The top gudgeon bushes are still fine.
It's a very easy solution if you have a small lathe, or know someone with one. I used 20-25mm rod, so I ended up with a flange that sat against the gudgeon under the bolt head or nut.
Hope that helps.