If you're handy you can fabricate one on your own, too. Just a spanner. Take off the barrel, fit the wrench into the bolt that holds the forend on and unscrew it. Slip the forend off of the action bars and replace.
I made my own fore end wrenches after I got my 870 Express. Wood, metal, or plastic? PM me if interested. $24 is a ridiculous price for one IMO. Things are a lot simpler for something you'll only use a few times unless you're a professional gunsmith and do a lot of swaps.
A forum community dedicated to defensive firearm owners and enthusiasts. Come join the discussion about everyday carry, optics, holsters, gunsmithing, styles, reviews, accessories, classifieds, and more!