How do I keep long grain brown rice moist?

According to Alton Brown, talking about why a short-grain rice salad won't get hard when cold:

But it won't be hard, the way, say, refrigerated Chinese take-out restaurant rice would be. Why is that? Well, long-grain rice, which is usually what's inside one of these, contains a very, very high percentage of amylose. [holds up the model] Remember this guy? When this cools, the amylose and water come together to make a structure that's kind of like, well, kind of like a crystal, which is why it's hard as a rock. The process is called "retrogradation", and it's reversed when the rice is reheated. Now since medium-grain rices have more amylopectin in them, this never happens in the first place, which is why I use medium, and sometimes short-grain rices for all refrigerated-bound applications.

If you can't heat up the rice, have you tried making some sort of short-grain variety?

I would suggest simply putting it in the fridge in small containers, which are also airtight. An airtight container means you're not losing moisture to the fridge. A small container means that there is less free space to contain moisture from the rice, so it will lose less.

Unfortunately, there's nothing you can really do to prevent moisture loss, just minimize it.

Aside form that, you may find it useful to cook the rice with a little more water than usual. I do this with wholegrain basmati and it works well.

The best way to reheat brown rice from the fridge and for it not go hard or dry is to cover with 1 sheet of very wet kitchen roll (paper), tuck in the sides and zap for 2 mins.... It really works I have been doing this for months now. You can also do the same with pasta.

I would try freezing your rice instead.

Maki on Just Bento recommends pre-portioning it, wrapping it, and freezing it while it's still warm to retain moisture. She also recommends using short grain if you find that even freezing causes your rice to become hard and dry.

I usually just portion out the rice in serving sizes (say, with a measuring cup) onto a baking sheet and freeze it. I then store the frozen rice in a plastic storage container. I haven't had trouble with doing this to long grain brown rice. It's usually eaten within a week.

I have never tried with long grain brown rice, but I have put basmati rice in the fridge many times. I try to use the most air-tight container I can find, and not keep it for too many days. To eat, I sprinkle a few drops of water on the rice and micro-wave it with the lid of the container on. That helps to make it soft and fluffy again..