Could you use tiny pellets fed in by a linear actuator and gravity, rotary loader, or some kind of a conveyor belt? If you want an off-the-shelf solution that's easy to reload, perhaps you could repurpose the loading mechanism of a machine gun to dispense the pellets.

What does your reactor look like? What fuel are you using? How are you getting to ignition?

Disclaimer : I know nothing about anything.

Hawking radiation ?

Laser tunnel ?

Magnetic canon ?

Centrifugal launcher ?

Vacuum diffusion ?

Electrical beam lensing ?

> Hawking radiation ?

That actually does make for a fairly efficient (better than fusion in energy per unit fuel mass) reactor design in principle, but you need a sub-solar-mass black hole (in the 1 billion - 100 billion ton range), and there's no known practical way to produce one.

Tesla valve?

Maybe the solution is in your fridge?

... Not being flippant; I find that these kind of prompts can help in thinking from a new approach.