I bought the Glencoe Corsair kit; it's a good starting point for the Gloucester, especially since you won't need to do much rigging -- the worst part of the kit are the masts (mine was warped) and the rigging blocks, which don't look much like anything except little undefined blobs of styrene. There is a fair amount of flash, as you would expect from an older mold, but the hull is very nice and the fit appears good with no major problems. The kit box itself has two more good-sized photos of the Gloucester that are different from the one you found on Wikipedia. Here are a couple more:
http://www.history.navy.mil/photos/sh-usn/usnsh-g/gloucest.htm
http://www.spanamwar.com/gloucs01.jpg
The info on the box states that the Gloucester had four quick-firing 6lbrs and I believe four quick-firing 3lbrs as well as a couple of machine guns. Here's a review of the kit:
http://www.cybermodeler.com/hobby/kits/glen/kit_glen_corsair2.shtml
If you do a Google search for "Glencoe Corsair II" you'll find it sold in several US online shops. It goes for $25-$30 US plus shipping; Trident Hobbies had the lowest price I saw, $24.99.