There are a number of vegetarian-appropriate setting agents on the market - among them agar-agar (powder, strips, or flakes from a sea vegetable), arrowroot (a starchy powder from the tropical tuber of the same name), guar gum (the product of East Indian seed), Xanthan gum (a corn extract), kudzu (a starchy powder from the plant’s tuber), and certain ground nuts and seeds. Most (but not all) kosher gelatins are also vegetarian.
Some of these are available in supermarkets, others require a trip to the health food store or even more aggressive hunting. Follow the directions on the package to see that your food sets up correctly.