On November 4th, Jimmy Gonzalez, a scout for the Washington Nationals has his annual South Texas Professional showcase in San Antonio, TX which is normally geared toward high school juniors and seniors. When my son went for the second time in 2009, they allowed about 10 guys in your situation to hit or pitch for all the assembled scouts before the high school guys started. This event is usually attended by most ML teams due to it's being a money raising event for a scout's family after he passed away at a young age several years ago. It is being held at James Madison high school in San Antonio this year. Information for registration is at jimscout.com.
I'm not sure if they will let a professional participate or if what they did in 2009 was due to special circumstances, but it wouldn't hurt to go to the site and get ahold of Jimmy Gonzalez.
Good Luck!