A good question! Mechanical devices malfunction for a reason, which I know is an obvious thing to say, however, a leak is fairly straight forwards to fix. Getting access and being able to do the job is another matter. If it was me, I would identify where the exactly the leak is coming from. If a crack in the housing I can help you with another housing complete. If the leak is from a seal or a gasket, I'd remove the box, strip down the assy and replace the damaged part as appropriate. There are a few tricks to removing the linkages but they are not that difficult. If you were local, it would be easier, I could show you what to do, but there are lots of Perente owners in NSW who may be close by and able to give hands on advice. Dr Google sometimes has "too good to be true" solutions and I'm a bit of sceptic. Mate, I'd risk manage your way forwards, small leak, - top it up and keep going. Big leak and/or funny noises in the box when turnng - time for it to come out! Land rovers are like well bred male hounds, they like marking their territory with oil!
Hope this helps? I do have a spare used power steering box if that helps -
Cheers STDDIVER.