I've been using a small canister of O2 for the last few years on summit hikes of Whitney and Shasta. They are available over the internet. A canister fits in your palm with or without a small mask, weighs just a few ounces, and provides dozens of deep breathes of highly concentrated oxygen. When you're struggling at high elevation, each breath provides a short but very nice boost in energy and mental clarity. The extra O2 has made the trips much more enjoyable. Before using a canister, I always used to get a headache.
These are especially great for quick trips when there just isn't enough time to acclimate. I bring a second canister if I'm base camping overnight above 10,000 ft.
I plan to try diamox sometime in the future to make a comparison, but O2 is natural and it solves the problem directly by providing exactly what the body is missing.
Note: if you decide to try this, plan ahead because they only ship via ground transpo which can take a week. They can't ship them by air transport, and you can't bring it on a plane.
