Ooh, this is fun.
Domestic animals are obvious: here that means dogs, cats, rats, a variety of fish, etc. The most "combat-worthy" is either a large dog or ferret.
Oh, and since this is Maine, you can get live lobsters easy.
Next up, invertebrates. I can catch grasshoppers, crickets, mantises, earwigs, silverfish, a ton of different kinds of beetles, flies, etc, etc, etc. Just go outside from spring to mid fall. In spring and summer, amphibians are easy: frogs, salamanders, etc.
Now, none of those are really "fighting" morphs, but you get a lot of stealth. Next up, transportation. Flight, of course. Who doesn't want to fly?
So, lawn chair + sunflower seeds + about a week = chickadee or titmouse morph.
For long-haul, mallard ducks are everywhere and semi-tame. I bet it'd be pretty easy to lay a hand on one. Careful, though, they
do bite.
I wouldn't mess around with geese, and certainly not swans. *shudder*
Once we've got those, it's off to
Maine Wildlife Park for a golden eagle, barred owl, fisher, and mountain lion.
AKA: puma. Oh heck yes, puma.
Maybe moose, too, just for the heck of it. Not a fighting animal by any stretch of the imagination--an adult can fight off coyotes and even wolves, but they present a large target and don't have very good senses. Dracon + Moose = The Way of the Dodo, I'm afraid.
You really, really, really have to think guerrilla to make the most of those morphs, but they're definitely accessible.
Get a mist net, and you can catch little brown bats, too.
Oh, and I like Dino's idea about venomous reptiles. You would have to find a zoo for sure; it's too cold for them to live in the wild.