QLD transport "approved inspectors" are generally safety/roadworthy certificate issuers, you may find some that do mod plates but very rarely, Mod platers are usually 'Free Lancers' and is something they do in their part time or companies that specifically do mod plates.
For example, here is a quick search i did, and this is what came up:
http://www.hotfrog.com.au/Companies/DB-Autotech
There are other ones, so its best to shop around, some will try to screw you by saying one mod per plate, but u can get some that put 4 mods per plate etc. The guy that did mine was a free lancer and he said he'll put as many as he can on the one plate, and cost me bout $80, but unfortunately, My iphone was stolen when i was in thailand, and i lost his number... Look around and just ask them when you get your quotes and make sure that they will give you the modification certificate/papers, because when you go to QLD transport, showng them a mod plate is no good, you need to show them the papers. Good luck wit it all!