Warning signage needed

I have received permission to trap on a couple large private marinas. Most sets will be cage style traps, however, I do image a couple footholds and body grippers (under the docks) will be used possibly. I'd like to post a sign nearby warning folks that traps are there and the animals could be dangerous. Any thoughts on where someone could get a sign or three? Maybe just make them myself?

Thanks

When you say you "received permission?" Are you doing this for free??