Is it possible tospray any kind of protective, clear paint on foam Tombstones?

my husband has some of those realistic, foam tombstones you can purchase in most discount and drug stores and he wants to preserve them, however, being that they are foam, we aren't sure what can be used on them to do that. Is there anything he can use to pray onto them that will preserve the look that already have?Is it possible tospray any kind of protective, clear paint on foam Tombstones?
hardware stores usually have a multi-surface clear coat spray next to thier regular spray paint. just make sure it isn't made exclusively for wood.Is it possible tospray any kind of protective, clear paint on foam Tombstones?
Some craft stores like Micheal's and Hobby Lobby have sprays that say ';Safe for Styrofoam'; but I don't remember seeing clear, altho is probably exists. An easier method might be to buy some water based paint-on varnish like McCluskys that is available in hardware and paint stores. It is not cheap, but a quart should do it for you.