I wonder if you could use some of those little tiny itty bitty pipettes? They are just a bulb and a tube, tiny tiny and only take a tiny tiny drop...
The whole thing is only about an inch long...they would be single use.
OT, you know what I'm talking about? We use them to collect blood samples from a pricked finger for use in glucose monitoring...
For now, I'll just use it straight-from-the-tube. A 10ml tube (about the size that lip balm comes in) is $6. I can probably do 100 knives with that.