Maybe small portions of different types of yeast? I know some people swear by champaign yeast, and say that they just keep the batch running like sourdough bread starter. In that case, they'd only need to start out with a teaspoon or so.
Unfortunately, I'm not DIYing very much right now, so I can't make any specific requests for myself. I'll keep floating things out there though. Somebody else is sure to see on of my suggestions and say, "I didn't even know I wanted that, but I do."
As far as syringes, I think the one I use most is the 10cc. I've used a thin/long 3cc in the past because its supposedly more accurate, but at that quantity, you're depending on your dilution being exact and constant throughout the container. I think its better to further dilute your mixture and use the 10cc.
Perhaps if you could find a source for really long syringes. I don't know what their medical application would be, but it would be handy to have one that was narrow enough and yet could reach the bottom of a seachem fert bottle.