PC-9 kits are a bit of a trick to come by.
Airfix had a 1/72 Shorts Tucano which I think is another PC-9 derivative.
There was a company (now I believe out of business) called Pioneer. I think they were British and they had a 1/48 Shorts Tucano in their catalog. I built their 1/48 BAe Hawk trainer and if that was any indication of the quality of their kits, its little wonder if they did go out of business.
If you're up for a challenge, I believe High Planes of Australia has a PC-9 in 1/72 in their range.