I have just noticed, while doing some routing maintenance and cleaning, that my 2010 XT660Z has a small coolant leak coming from behind the lower nut embedded in the coolant recovery tank. Efforts to locate a replacement tank have so far yielded nothing. I see this is not an uncommon issue, possibly due to overtightening. Is there a viable fix if I can't find a replacement tank? I don't want to have to silicone the bolt in place.

you could use a two pack adhesive....