The only ones I have ever seen were custom made. Mind you, with a fresh set of bushings in the stock shifter, that can be a major improvement. I will try to find the part #s for the OEM bushings for you.
The only company made shifter was built by C's from Japan. They have been out of production for around 10 years now. You can fit a BG8Z C's shifter as well but they have been out of production for around 6 years now.
I have seen a few custom built short shifters people have made but I am not sure how well they worked out.
I made seven short shifters by pressing the ball up about an inch, even had them powder coated and ordered new dust boots. They are for the 2WD though. If I had a GTX to look at I bet I could come up with something. I'm not sure there's even a GTX in Boise anymore.