where can I get  the anti-lock brake system for my mitsubishi 3000gt 1993 sl?

I'm looking for  the anti-lock brake system for this car. I recently bought it  and it has began to act up. I can drive it because when I put it  drive it locks and i can move it it will release but then it would lock again quickly. It has new brakes and a new master cylinder. I have done everything to this car already and I don't know what it could be now.