there are wrenches you can buy (cheap) to do it. normally they are just stamped out of flat steel and available at HD, Lowes, Ace, just about anywhere. last one i bought was less than 10 bucks, i think it was 5.99.
or you can borrow one, because really-how often do you need it as just a homeowner. If you were close, i'd let ya borrow mine! It hasn't been used in over a year
Try Harbor freight, it'll be made in china or singapore but it'll be cheap anyways, and how many times will ya need it. I hate to buy anything except USA made, but on something like that i usually buy whatever's cheapest. Or you could use a pair of large channel locks.