If you live in California or anywhere with a mediterranean climate, chances are, you might be able to cultivate this plant outdoors year-round as they appreciate cool temperatures at night year-round. These plants can die in a matter of hours in hot and humid conditions with little air movement. R.dentata grows inland in S.Africa where temperatures are hot during the day in the summer. R.gorgonias is found near the coast and appreciates cooler temperatures and higher humidity than dentata.
Silverhill Seeds offered dentata seeds a couple of years ago, but hasn't offered seeds in recent years because a fire swept the area where the dentata grew. It might be a while before seeds can be collected.
Seeds of R.dentata and gorgonias are difficult to find, and in the case of dentata, the seeds can be very difficult to germinate. I would treat the seeds of dentata like tuberous Drosera or Protea in order to replicate the natural conditions of its habitat. This means sowing the seeds on a pot during a hot and dry summer and wait till the cooler conditions of winter before watering. R.gorgonias is much easier to germinate. Sow the seeds during the winter when conditions are cool and they should germinate within a couple of weeks.
As for shipping plants, it might be possible if the plants are seedlings. Last winter, a couple of my gorgonias seedlings were uprooted after heavy rains. I repotted them and they grew fine.
The symbiotic insects are interesting, but impossible to find in the U.S. and are even more difficult to raise than the plant from comments by another grower. These insects are highly sensitive to insecticides.
I grow both species and they are very slow growing under my conditions, although I have heard of gorgonias flowering in a year from seed.