If you are looking for something akin to high energy, full tilt sparring, similar to most hard styles and MMA systems, I don't believe you'll find it. My limited experience hasn't turned that up under the TaiChi name.
But, I have sparred against Tai Chi practitioners, in one case it was explained to me that the reason I was resting on the mat was due to something to do with a Lute and a Horses mane, LOL!
Bob is correct. But be aware that not all Taiji teachers teach, or even know the martial aspects of the form. As you may be aware, each posture in Taiji has a martial application and many applications can be applied to different forms of attack. For instance "Grasp the Birds Tail" can be two arm locks followed by a press and a final push away. There is also a two man fighting form where partners attack and defend using the Taji postures in sequence. There is also "free form" where partners attack and defend at full speed. However in all these practises Taiji principles must be strickly adhered to.
Though most do not teach "fighting" aspects of tai chi, the few that do usually do more controlled and slow moving drills.
but tai chi does have fast drills and we "spar' quite often, including striking, throwing, and locking techniques. just like any "martial" art taichi incorporates fast sparring, hard sparring, controlled sparring, and free drills and sparring, into its methods.