You'll have to find them around the neighborhood. Check with friends, family, and neighbors. Be very careful that you don't feed anything with pesticides or other toxic chemicals on or in it.
Here is a list of things to look for:
Mulberry leaves
Grape vine leaves
Hibiscus leaves
African hibiscus leaves
Blue hibiscus leaves
Rose of Sharon leaves
Rose leaves
Geraniums
Gazanias
Lavatera
Pansies
Petunias
Hostas
Honeysuckle
Cape honeysuckle
Leaves and blooms from any squash plant, like pumpkin, cucumber, summer squash, etc...
Young spineless opuntia cactus pads