Former L.A. Lakers coach Pat Riley had the best record in NBA history, but the two things fans ask him most are: How do you do your hair and where do you get those clothes? NBC’s new basketball host primps with ”water, Sebastian High- Contrast Gel, and High-Contrast Hairspray. The whole thing takes about a minute and a half, and you couldn’t mess it up with a sledgehammer.” And the duds? ”Ninety percent is Armani.” When the maître d’ in his Park Avenue hotel dining room handed the coatless coach the ”house” jacket — a navy sport coat — Riley said forget it and called room service. How will he ever don that fabulous NBC blazer?