For cactus and many types of succulent, Mesa Garden is the best source for seeds. Seedlings will start out well in a terrarium but adult plants need somewhere with better ventilation, better drainage, and less humidity.

If the humidity is high in your terrarium/vivarium, consider growing Bromeliads, as they are more suited for humid conditions, as well as lower light.

i have been looking at this site

Here is a link that might be useful: b and t world seeds