Tuning Keys for Zither Pins?

I am planning to start selling an instrument that uses zither pins. I probably should provide a tuning key with the instruments. Thus far I personally have just used a tiny crescent wrench myself.

Do you know of a good source for tuning keys? I would be willing to buy them by the dozen or maybe even a larger quantity if it got me a decent price break.

I do have some ideas for making a key, but am not sure if they will pan out.