Such things exist, they're called coolant inducers, however they are a bit pricey, and I've never heard of one that would be small enough for a Sherline.
Most mills that need coolant through the tool use through spindle coolant. It's a feature typically in large VMC's though.
If you had more time and inclination than cash you might try that method and build an inducer to run water through a hollow drawbar.