Your best bet is probably a junkyard. These pulleys are not easy to pull off, you may need an impact wrench, a vice and some tool or some way to hold the pulley from turning. And a puller tool, a 3 jawed puller might possibly work but the proper puller tool is better - there is a risk you can wreck the pulley with a 3 jawed puller.
Unfortunately you need a pulley the EXACT same diameter of the one you have, or else your belt wont fit. If you can buy a burned out alternator it may save you money because all you want is the pulley - but ultimatley you might have to even get another alternator if the part is not available seperately -