It's easy for anyone to purchase one of those high visibility vests...I wonder if the fragment is actually from a Waste Management vest, or just a plain, unmarked vest without a company logo.
Agreed, many sources for safety vests:
Big box home improvement/building supply stores (Lowes, Home Depot, McCoys, etc).
Hardware stores (Ace, True Value, mom & pop, etc).
Sporting good stores (big box, like Dicks, Sports Authority, running or cycling stores).
Truck stops.
Online.
And as someone else mentioned -
safety vests w company-employer logo from utilities, state-road depts, etc,
so current or former employees have or may have.
JM2cts.