The hornworms/hawkmoths/sphinx moths (family Sphingidae) are a big group, but the most readily available species is the tomato hornworm. You'll need a healthy patch of tomatos (good news for you, tomatos are easy to grow) and a mesh enclosure to go around them. Are you doing this for fun or do you want a steady supply? If the latter, the necessary operation will probably be too large-scale to be worthwhile. If you just need big, soft-bodied insects, consider breding one of the larger roaches instead; they don't require a whle garden to themselves.
Sorry, I'd forgotten about the tomatine accumulation. You want to contain the whole life cycle? I don't know how much room you'll need. It will depend in part on whether the adult moths can be convinced to feed on prepared nectar solutions; otherwise your container will need to be big enough to enclose enough nectar-producing plants for all the aduts. I would guess most commercial producers just collect eggs from wild moths for each batch of larvae rather than trying to keep a continuous lineage going. If you make the foodplants available, you will probably get eggs; no need to keep the adults enclosed.
Most will feed on prepared nectar, they just need enough room to hover above the food source, if they can't they won't feed. I was think about getting the 18"x30"x18" flexarium mess cage.
Let us know how it goes. Do take care that there are no gaps through which parasitoid wasps could enter the cage. They could wreck your operation pretty quickly.
They would be housed inside anyway so I'm not to worried about the wasps. Oh, and if I were to find some wild hornworms, if allowed to pupate, they would be safe to breed as moths right? The toxin doesn't transfer to the eggs does it?