Amazon has all kinds of reflective tapes - various colors and widths. Only fly in the ointment that I can see is the price and the need to buy a full roll (it doesn't come by the foot). Ok, somebody will make a liar out of me - I did only a cursory search when I was looking.
I forget which member here work(ed)(s) in a sign shop, @kiltman(?). Anyway, whoever it was suggested to me to hit a local sign shop and they might give me roll end pieces for free or a few bucks. My local place (that I've used before) was charging full boat for a tail end scrap of black - the guy said they use scraps to punch out reflective letters. Of all the signs they had on display, I saw none with reflective letters.