A little update to my situation:
It seems that the tongue of the Teryx seat belt is larger than the standard car one. The Teryx seat belt is basically the same size as an older Chevy vehicle up until 1999. The tongue is 1.6 (1 5/8) inches wide, the standard size for most modern vehicles is 7/8 inch. Most of the extenders caters to the 7/8 size and also to the sizes the airlines use. Both of these are different than the Teryx. There are places that make an extender that should fit the Teryx, the website seatbeltextenderpros.com has one called the Type G variation that looks very close to the Teryx. It describes the dimensions and they are almost exactly the same as the Teryx tongue, but it does say that the tongue can't have "shoulders" on it, and of course the Teryx one does. I was going to try this one, but i decided to hold off since I found a work-around.
I went to the local auto parts store and bought a 12" extension, but this one extends from the bottom anchor point on the belt side. Simply remove the bolt holding the bottom of the belt to the side of the Teryx and bolt the extension in, and then bolt the end of the seat belt to the extended piece. 12 inches was too much for my purposes so I tied a knot in the extension and that shortened it enough.
There are two downsides to doing it this way. First, you can't just unbuckle the extension to remove it if someone else sits there. You have to get out the tools to remove the bolts. Not a big deal and probably takes 5 minutes. Second downside is that where the extension and seat belt ends bolt together sits right against the outside thigh of the person in the front passenger seat (location of my extension, but would be a problem wherever it is installed). Because of this I used some padding to create some protection for my passenger. It works great and my mother in law sat in the seat with the belt buckled in comfortably. This solution works for me since I will probably only use it next weekend on a Poker Run. Once we are done with that, I will remove it and only re-install it on rare occasions. If I needed the extra length all the time I would contact Seatbeltextenderpros.com or someone similar to see what they offer.
I did notice that smaller tongues such as animal seat belts (usually 7/8") will plug in with no issue to our larger buckles, it is the other way around that causes issues. The 7/8" extension will click into the buckle, but our larger tongue will not fit into the smaller 7/8" buckle.
Wow, that was a long-winded explanation for a situation that 99.9% of Teryx owners won't run into, but if it helps one person out, it is worth it. Also, I fully expect someone to offer a much easier solution that will make me smack my head and call myself a dumbass.