Reflective tape can be bought from a sign company locally. Probably the best bet if looking for larger sheets.
There is Utah Barricade on redwood road. 3232 S Redwood Road, Salt Lake City, UT 84119 tel:801-973-9800
Wasatch barricade. 4185 W 8370 S, West Jordan, UT 84088 (801) 282-0000
There...