Well, I went down to the Bellevue WA Kinko's & made a 24"x36" copy of "NOW inspections are working". It was $2.00 for a single copy on the large-format copier, but it was black & white only. I had to re-do the "NOW" in white with a thin outline, then I filled in the red with magic marker. They quoted color copies at several $$$/sq. ft., which at 2'x3' (6 sq. ft.) would be pricey, plus it was a 1-day turnaround.
I got a 3-pack of 30"x40" foam core at Office Depot for $13.00, and a couple rolls of plain transparent contact paper at Home Depot for $13.00. (I only needed one, and these will last us through several campaigns.)
The result looks great! I'll be making up a couple "Dictators (love) Appeasers" tomorrow, probably in 16x20, and filling in the heart by hand.
Here are the B&W templates, if anyone's interested: