Hey g'day,
From what I understand, having HID bulbs / upgrades in a car that was never designed for HID lights is illegal. I don't know if it is state by state or against the Australia Design Rules. To have HID I think you have to have self leveling lights (i think i read somewhere - correct me if I am wrong) so you don't blind other people. This is especially so if your 4x4 is raised. If your lights are illegal and you cause / have an accident then you may be liable to face court on the matter. Also your car would be deemed to be unroadworthy by the department of transport and you may not be covered by your insurance.
You can definatly buy a new set of headlight lenses and upgrade the power of your bulbs but as the others above have said you may be far better upgrading your wiring loom.
You can buy ready made sets from 4x4 shops (brands like pirhana and terrain tamer, etc) or you can get thick wiring and wire some H4 plugs and make your own.
Run the power from your battery to a relay for each beam (4 all up) (low beam by two and high beam by two) then from the relay output pin to each power pin on the h4 socket to your bulb (high, low & high, low). Your negative from the negative h4 pin to the battery negative. Next you can cut your old wiring or buy male h4 sockets to run your normal power pin to your headlight to each relay switch pin to tell the relay to allow the power through (this is so when you turn your lights on the normal power that would go to the bulb which has now dropped in voltage over the years will go to the relay and switch it on. The power will then be allowed through the relay directly from your battery to the new headlight socket with new, thick wiring giving you good output for your headlights). The negative pin from each relay can be returned to the battery negative or earthed to the body.
There are a heap of diagrams and instructions out there that explain each step in detail and I know my response is a bit hard to understand if you are not familiar with this type of thing but I am in a bit of a rush at the moment sorry.
I would google headlight wiring loom upgrade and you will then be able to see home made and bought ones. I found a good one a while ago from a jeep forum in the states I think. I know it is not a patrol but the principle should be the same on any car where the car has a constant negative with the power pin dictating the power going to the bulb. I don't know if there are any patrols that switch the other way (Posative switching as opposed to negative switching is something that the other more electrical people can explain indepth).
I hope this helps.
Cheers