Meggy and Hawkeye said it best. Start off tactfully. Tact is the ability to tell someone to go to hell and have them look foward to the trip.
Tell him you undrestand that a sudden stressful situation sometimes causes people to do stupid things, like leaving the scene of an accident. Ask him what we can do to avoid all the trouble of going through his company's insurance for hit and run, etc., with your witness, police report, etc. Let him know how understanding you are, not wanting to get him in any trouble at work for his wreckless use of company vehicle. You just want you bike like it was before.
Let him think its HIS solution to pay through the nose, cash, for new plastics, scratched paint, scuffed shocks, steering damper damage, dented D&D muffler, bent clip-ons, damaged chrome mirrors, carb rebuild because of being sideways, FOD damage to the stator vanes in the jet intake.......you get the idea. Have an official estimate from a stealership. If he gets mad, or blows you off, be even nicer, expressing a true desire to avoid "all that legal stuff. " Never say the word 'sue', because this makes people feel cornered and lock up.
Hopefully he learns that hit and run will cost HIM PERSONALLY three times what a little accident report would have.
You can always play hardball later if you must. Plus, having made a good faith gesture and a record of always dealing tactfully will put you in an even better position if you do have to go to court.
Don't forget to do something very, very nice for your witness who took the time and trouble to wait for a stranger to come out of the gym. And you could even invite her to Strat's where a whole group could sing her praises. Such people deserve blessings.