Doing a quick check, the type has an FAA type certificate, as well as a CASA one. To obtain a TCDS, the original applicant should have obtained the data you need. I'm surprised it isn't in the POH?
If, you asked a reputable FTE to carry out the testing to prepare the data you need from scratch, I doubt you'd get change from 25 hrs testing, and depending upon what was required, you might get as far as 100 hrs. This, plus the write-up work, would cost you a fortune - it's just not worth trying.
If I were you, my first point of call would be Fairchild or the FAA, they should have produced all the data for FAA certification, and that should certainly be acceptable to CASA. At worst you should only need to top and tail some of this data, perhaps taking some of this and producing specific charts for your own company's operations, and wrap it up into a company operations manual.
If you want some steers on how to manipulate the data into a suitable operations manual, the old British code "BCAR Section K" as well as the CAA document "CAP 385, Specimen performance Charts, Group A" will help you through it. There may be CASA or FAA equivalents, but I'm not sure where to find them. (CAA docs can be ordered from Documedia,
http://www.documedia.co.uk/
Unless you love the maths, you might be better off employing a consultant who can prepare the sort of charts you need in a fraction of the time. I do this sort of thing if you get really desperate, but if I read your address correctly, we're opposite ends of the planet, and you might try contacting John Tullamarine, who can almost certainly point you at somebody qualified to handle the task for you (with the added advantage of that somebody probably being known to CASA already, which is likely to help).
G