Being in a major centre like Melbourne you should have no trouble finding a stockist of nitro.

A lot the builders here in the forum have a liking for poly-(urethane) especially the wipe-on variety and they're getting some great results too ... haven't used it myself so I really can't comment but suspect that its due to it being cheaper, easier to work with and less "unfriendly" to the human system ... (guys, anyone want to provide advice/opinion on poly?)

There are just a couple of things to be aware of for using nitro ...
- it can be less forgiving than other finishes (but a bit of care and attention to deal generally overcomes this factor)
- make sure your area's well-ventilated (inhaling nitro can be nasty to your body)
- Always go for lots of thin coats (almost "dusting" coats) rather than just a couple of thick coats - this is the area in which its less forgiving than other finishes (where you can get away with thicker coats) ... but the up side is that you don't need to wait days for nitro to cure between coats as it dries pretty quickly (depending in conditions you can get in two coats in a day) ... and the difference between thin-coat/thick-coat approach will show in the final finish
- after you've got enough coverage in your coatings, give it up to a week (or more - all depending on ambient temperature) to fully cure and harden before polishing
- I "wet" polish the cured nitro by hand (I don't have a polishing/buffing wheel) with a 2000+ and 3000/4000 grit wet&dry and using Windex for the "wetting agent" (yes, Windex! - it seems to make quite a difference over using just water) ... a bit of "elbow grease" in the polishing and its not hard to get the same level of finish as on the top level, big-name guitars.

(DB - please forgive me for all this conversation on the "naughty" n-c stuff! )