Leaking A833

Ohhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh, that is a common source for leaks. the cure is a new expansion plug. This one can be reused if it falls out, but that rarely happens; you usually have to dig them out by drilling a small hole and pulling it out with a screw. It's just a common expansion plug.
But since you are half-way round the world,if you can't find one locally, that's just what I'd do.
Drain the oil,dig it out, tip the tranny over backwards and clean the area up;OIL-FREE.
Take the expansion plug and restore it to its proper saucer shape.Fill the hole in the plug, either brazing it up, or soldering it. Grind the mess off, especially the backside. Reinstall it with some locally available sealer preferably not RTV. RTV is OK if the area is exceptionally clean. Oil will be in the space around the cluster pin, and is all too eager to travel uphill by capillary action or creep. It is very difficult to make oil-free, and keep it oil-free,long enough to install the plug with RTV. So, I prefer an anaerobic permatex, or a shellac-type product . To install the plug, you just lay it in the shouldered hole, and smack it with the ball end of a ball-peen hammer, or a large flat punch at least 30% to 50% the diameter of the hole,like a 1/2 inch bolt.The flat end of the hammer will not sink the center deep enough. The center should be slightly depressed when you are finished.When the saucer goes like that it will be expanded into place, and the loc-tite will both keep it there and seal it. Give the plug a couple of bops.The area behind that plug will eventually fill with oil.
Let the sealer set,
refill, and install. Good luck.
FWIW
When I used to rebuild those, and all the parts were fresh out of the parts washer, and superclean, I installed new expansion plugs dry. I never had any comebacks in over 5 years.