My bet is it will be one of these:
Bloomberg
Oprah
Al Sharpton
Jesse Ventura
No way he would pick Ventura or Oprah. Ventura would compete with him on ego and insanity,and even kick his Mama's Boy ass. Oprah would be more popular AND has more money,so that would rule her out,too. Especially since she started with nothing and earned her money.
Bloomberg has enough money to hire Trump to wash his car,so Trump won't pick him because he can't stand the wealth comparison. Plus Bloomberg might have bigger hands,and there is no way Trump is going to pick a running mate with bigger hands.
Sharpton is a possibility,but they are both denizens of NYC.
Maybe Cynthia McKinney,the insane black racist ex-congresscritter from Ga to bring in the black southern and Whymen? vote? She is almost as crazy as he is,so that might be a plus from his POV?