While we're on the subject of drills, what about dental bits? I've used them for years.
If you're cheap, or smart (depending on point of view) ask your dentist to save his old bits for you, next time your there.
Not only will they be cheaper (probaly free) but, since they are too worn to properly cut enamel, they're worn enough that they won't tear up plastic. And they go down to #80 (.0135")
If you're feeling rich, hit a dental supply house. But be careful, new bits will cut through plastic like a hot razor thrue soft butter. And they ain't cheap.
You'll be amazed at the number of different cutting shapes and styles, that are available.
I don't suffer from ulcers, I'm a carrier.