I would go for the outdoor plants personally. You're right in thinking that normal indoor ones would be no use, they're really not designed for spraying. Also the outdoor ones should be better put together so they can survive being our in the wind etc.
Silk leaved plants (get greenery, not the types with fruits or flowers) with plastic covered wire stems hold up fine. I use them all the time. Those fake Ficus trees in baskets work in free ranges, but they are usually planted in baskets with Spanish moss. You'd have to protect them from water.
I got a whole bunch of fake plants and vines from the dollar store, just wash them with soap and water first to get the extra dye off. They are super cheap too
I got a whole bunch of fake plants and vines from the dollar store, just wash them with soap and water first to get the extra dye off. They are super cheap too