I've got a sub-division going in beside me.  I'll have 112 new next door neighbours.  Sigh.  I'd like to plaster the trees along the common 1/2 mile boundary with No Trespassing symbols.  That's a red disk 10 cm in diameter.  Of course, I'll put up a few signs, too, but at $4 each, I'm not going to get too many of them.  They just get vandalized anyway (been there, done that, even before the sub-division was in the works).

Anyone know of a supplier of such disks?  I'd make them myself, but I don't generate any food tin lids of sufficient size (cat food tin lids are too small).