at the Tang Soo Doo school I used to go to/teach at we did a fight night every Wednesday night after all the classes were done. We get some tape, put it on the floor to make a square or circle, then 2 people go at it till one of em is down. I did a few but I'm not in shape for that anymore. I was 6'5" 275, now I'm 325 . . . so no more for me thanks! But look into getting a college or karate school involved and legitimize it. But if you want to stick to street fighting, then you will have to keep it on the street. Legitimate organizations will want protective wear and what not to keep their liabilities down. Even if you sign a waiver, the company can still be sued/held liable, esp. if it's illegal street fighting.
just my 2 cents