Snow Peak Solo cookset fits around a Nag. bottle, and also fits the bottle and into a Maxpedition Jumbo bottle holder.

"Lightweight and durable, Snow Peak's Mini Solo Cookset can accompany you anywhere. Titanium is more corrosion resistant than stainless steel, and more heat resistant than aluminum.

Set includes:
One 4 1/4in. x 4 3/4in Pot. Vol. 28oz.
One 10 ounce cup.
Nylon stuff sack.
Weight: 5.5oz.
"

I agree that I am not sure how often you can use a nalgene in this fashion before it fails. I would certainly not recommend using this method as a common practice, but in a pinch, I'd drink the water. The amount of bad stuff coming out of the lexan should be low enough for brief exposure.

It is interesting that the same container that I used has written on it that it is microwave safe, which would imply that it can be used to boil water in a microwave. I haven't tried that, but I am sure it would work. I'm not sure why anyone would need to do that though, since if you have a microwave you probably have access to better cooking container choices.

Try and stay cool out there!

Greg