Have you considered using Employee Health, who are responsible via OSHA to minimize employee risk, monitor exposure stats and write policy to work with the medical director, and they, well in my place, would be the ones responsible for a policy initiation that requires the docs to properlly dispose.
Now this piece of paper does not give you automatic compliance, but once you identify the repeat offender, all your leverage is there before hand. Let's face it, the doc's leaving the sharps out are for the most part the ones that will require the chain of command, or at least several verbal reminders to the existing policy.
My hospital holds every MD and nurse accountable to policy. That's why once we've gathered info that something is a problem, proceed with policy and educate staff once initiated.
Personally, I know the few who leave a swan or cvp tray full of sharps at the bedside, a few years ago I started to say "Can I place the dressing while your cleaning up your sharps?" and when the knuckle head dares to say "take care of this...", looks at the sharps, never makes eye contact and darts out the door.... YES I do approach him and say "you don't intend to leave your tray of sharps at my patients bedside do you?".(spoken in the help me to understand this situation voice )