Well after weeks of waiting for parts the first steps to getting everything back together were made today.
These are the little f***ers that get loose over time:
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Partnumber TYP000010, still available at Land Rover. I bought new ones as they include a wavy spring washer, which on the old bolts might have lost some springiness. Didn't want to take a chance on these. I also degreased everything and used loctite on the threads. Not prescribed by RAVE but less likely to rattle loose.
Another issue was that this parking gear together with the sensor trigger wheel doubles as an oil sprayer for the output bearing. The sprocket slides over an O-ring on the shaft, and the collar you can see on the picture above around the shaft hole slides over a piston ring type seal. This creates an oil chamber and a small hole in the sprocket allows oil to spray onto the bearing. For this reason the o-ring on the output shaft needs to be replaced, this is STC4602 which is not produced anymore, not by LR or aftermarket brands. I settled for a 25x2mm FPM o-ring which was the closest match to what I think is a 1"x5/64" O-ring.
Did you try Wych Bearings? They've always come up trumps for me.