Well, I finally got my chains on and installed. It turns out that the Wesco site I linked in the first post only ships within Canada. Their sister company,
Bluejay Industrial, ships to the US. The Bluejay site did not show the square link chains as available, but when I called, they do have them. I ordered their 14ATV–610SQ "Square Link Alloy ATV Pattern Chains". That was the size that showed up on the Wesco site for my 27x9-12 tires. The guy at Bluejay recommended the next size up for my tires 14ATV–615SQ, but said the 610 size should fit. It did fit, with a little bit of fussing to get it on. Once on the fit is great. He did say they normally don't run bungies or chain tensioners on their diamond pattern chains (which is also what the manufacturer of the similar pattern chains on my tractor said.)
If I were doing this over again, I'd order the larger size. It would probably be easier to get on, but these are easy enough.
The next accessory will be the Moose 2" receiver, but I have to wait for Santa to bring me that one.