High-Vis wool, baby!!!!
http://www.joneswares.com/item/Men_s...ersey_/268/c61
Available in short or long sleeves, and without pockets and zipper as a running shirt.
ETA: uh-oh, I posted the men's link. Here's the women's: http://www.joneswares.com/item/Women...ersey_/299/c70