I'll be growing them from seed shortly. The best (easiest) source of seed is the Gesneriad Society, but you have to be a member to have access to their seed list. It's quite extensive for species and hybrids. I bet they have seed from 1000 plants (I'm looking at the list).
http://gesneriadsociety.org/ Also a lot of members of local and national African violet clubs have seed from various gesneriads. I found that joining one of those groups was worth its weight in gold. You have access to all kinds of plants that aren't publicly available.
