We used a
Streamlight Polytac HP last year for targeting. The HP has a small and bright hot spot with a good throw, making it good for this use. The whole head of the light screws off and it
can be wired directly to the regular
5V converter.
For that whole distracting the drivers thing, you can turn the light on and off depending on when you want to aim and shoot. Just set it to a button for momentary on/off. You'll also want to mount any light you pick inside a tube or something to block out the spill so you don't blind opponent drivers under the goal.
Just be responsible with the light and you shouldn't have any issues, but just like others said, others can always complain about the light. We didn't have any problems at the two regionals we attended last year. We found that our photon cannon was way less distracting than those ridiculously bright LED rings.