I would strongly discourage trying to build your neck strength against chokes by "simulating" a choke. You may learn a tolerance of choking, but you're not going to build muscles where there are none. And you may find yourself on a quick trip to the morgue via accidental strangulation.
The neck rockers and similar devices can still be found in some gyms -- but take 'em easy. It's not hard to overdo something like that, though it's good that they move through a range of motion. Same thing with straps to hold weights...
Isometric exercises, either using your own hand or a towel, aren't bad, though they suffer from the weakness of all isometric exercise in that there's no motion.
You can also slowly and carefully work with a partner to resist the motion. For example, you can lay on your side, and as you push your head up, your partner holds it down and slowly lets you move it up. (Kind of easier to show than explain...)