Picked up a 3 of these (they come 3 to a package) at Auto-zone.
http://www.autozone.com/autozone/acc...er=295537_0_0_
Pulled over to help a Class A who managed to get himself stuck in a ditch and realized I had no flares or markers of any kind. So I went out to get some flares. They weren't what I went in there for, but for the price they seem to fit the bill.
I put one in each vehicle and the trailer.