Any pushbutton call can easily imitate a fighting purr. Just make it purr harsher, or rougher, or more aggressively than you would when you are making a "contented" purr. To imitate a fight, use two.

You can do the same with a mouth diaphragm, if you can purr, by, again, making a more aggressive putt.

I use the K & H fighting purr system (2 pushbuttons) and also run a mouth diaphragm, with which I putt, purr and pop, while using the 2 pushbuttons to aggressively purr.