There doesn't seem to be a whole lot of interest in the subject. I use small aquariums for tender bigonias and epscias in the winter, and keep a two gallon octagonal plastic tank on my desk year-around. I also use rose bowls to grow tiny sinningias - they bloom well and set seed.
Give your jars a try. Use potting soil as a medium and cover the jar. If you like I can send you a tuber of a small sinningia - plant grows only to the size of a half dollar. I'll dp it at no cost to you since we're talking less than a buck or so. Let me know via D-mail. Hank