An SKS will be a great gun to take with you.
I wish I still had my 20-round modified Paratrooper.
In general, I prefer rifles to shotguns, but this is one case where a $100 single-shot H&R or Rossi 20 or 12 gauge might be hard to beat. Throw a buttcuff on it, add a sling, and practice some.
Huh. Actually, you can get a Rossi 2 or 3-barrel combo very reasonably, too, and then choose whether you want rimfire, shotgun, or centerfire. Not bad choices, any of them. In
the 3-gun, you get .22, 20 gauge, and either .243 or .44 magnum, all for about $300 new, in a fast-handling little package with synthetic furniture.
Another option, will be about the most practical reason I could see to buy a
Sub-2000. You can carry it folded, with loaded mag, in a case on an ATV or in a truck. In an emergency, you can be GTG in less than 10 seconds: fold fore-end down, rack bolt, engage. You may be able to find one for as little as $300.
Another compact option for defense is another firearm I wouldn't typically suggest, but which would work fine for packable defense in/on an offroad vehicle: a pistol-gripped pump shotgun. You should be able to find one new for no more than $200, or you can buy a used one and just put a PG on it. Be sure you've got at least 26" overall length, though.
You don't want to look like a Mad Max reject, tooling around with a strung longarm on your ATV, and if you look like you're prepared to hunt, you may be in trouble with Dept o/ wildlife if it's not season. Keeping one of the low-observability options in a case on your ATV or out of sight in a Jeep may help
keep you out of trouble, as well as get you out of trouble should you need it.
John