Another forum I'm on found these somewhere and modified them slightly to include the statute number for Missouri. Since we added the legal-ese they'd only apply in Missouri but I can send you the Word file if you want to modify it.
posting it on your home or vehicle may also make you a target for thieves. a Pro-ccw sign marks the home as containing firearms and ammo, thusly creating a draw for a thief. conversly, they may shy away because of the fact your home is armed, until you leave home.
If I owned a business I'd certainly post one, but I wouldn't post one at my home either. I imagine a lot of businesses would be reluctant to post such a sign for fear of liability.
Even in Alabama, where CCW is legal, I don't see a lot of signs encouraging CCW (sadly). The cloest thing I've see to that here is at a Sporting Goods chain that tells you that guns brought in must be brought in without ammo and must be checked at customer service, then says "this does not apply to valid Concealed Carry permit holders" or something like that.