Welcome to the forum, Joe.
The standard turbo is a good choice for replacing it because then nothing has to be figured out, adjusted or fiddled with to make it work. Niss4x4.com.au can help with second-hand ones.
There are turbos for sale on e-Bay that you might consider. A few people on this forum in the past have bought them and have had success - you could even see better performance, as technology and materials improve, you get better flow rates and faster spool-up times. But as always with items from eBay, you may also end up with something unsatisfactory. I think using Paypal to pay for items helps there though!
Going too radical (high boost) could see your EGT rise too high for the engine, so you'd want to investigate an EGT gauge as well if you were looking for something that gave you a lot of extra boost.
If not already fitted, an intercooler is a great addition as well - more for its insurance value in case of turbo failure than the performance gain (which is minor, but it will be there).