Are you wanting to dose that small of an amount on a regular basis? If so, it really is much easier to mix up your own liquid ferts and use some sort of dropper. I always prefer to measure the cap of whatever bottle I'll be using, and then mix up the ferts so that one capful is my target dose.
Any easy-to-use volumetric measurement of 0.1 gram will be rife with inconsistency.
Originally Posted by Optix
look on ebay for a jewelry scale...theyre cheap too
I bought a scale on ebay for $20/shipped that weighs 0.1 grams up to almost 1.75 kg. Really great buy. I use it for fertilizer measurments and for homebrewing (not without a good wipe in between).