Agar is available at most bulk health food shos as well as many on-line sources. Agar is inert, has no calories, and has a desity close, to many amine powders. Agar is derived from seaweed, and is used in candy making and cooking, as well as micro biological and medical laboratories. I know your orginal query stated that you didn't wish to use fillers, but they have a few advantages.
1. You are able to have the exat amount of powder necessary to fiull the capsule, and you will premix this ratio, so when capsule filling time comes, all you have to do is fill each capsule.
2. High speed capsule filling machines can be utilized, these are used by hand, you insert half of each capsule into a hole, and then the powder is scraped across a plate and falls into the waitng capsules, then you place the tops on tha capsules and they are done.
3. If you are worried about consistancy, run through a mesh screen #100 works well, and the powders will sift together. Then you use this mixed owder to fill the capsules.
4. This works very well.
Also #5 capsules are available; however, the smallest lot I have seen them sold in is 100,000 units.

Quick Capsule filler