Keep a TT with a small bag of phony blood next to your front door. It only takes a second to load, and then you can make the red stuff appear to come from anywhere. You can preface the gore with some sort of joking curse, such as, "If that's not true, I'm sure the Almighty will send us a sign."
If so inclined, see some of Joe Nickell's writings in Skeptical Inquirer for tips about how to make stigmata seem more shocking than it actually is. As Joe explains it, a little blood can go a long way.
The TT with phony blood, by the way, was a gimmick used by one of our buddies (his name rhymes with "brandi," and it ain't John Candy, Jessica Tandy, Jack Handey or Fred Grandy) on a certain late-night national television show. If it's good enough for him to gross out the entire USA, then it's probably good enough for you to scare the excrement out of some religious pests. Just be sure to hose off your front step after they run away.