I did a Nexttag search, the prices varied quite a bit. Ended up buying on amazon for 75 total. It looks like http://runnersgear.com/page/R/PROD/PLI-002
is the best price though @ 62.96, not including s/h. There's a cleaning solution to use with it, on this site it's sold seperately, I probably would have saved money on this site, b/c mine came with a small sample.
This thing will absolutely increase the oxygen levels in the blood. It's probably one of the most profound ways to increase oxygen levels, if you don't mind doing it the old-fashioned way. Most people are shallow breathers, myself included, and I had forgotten what it felt like to take a really deep breath. It's an incredible luxury...my heart rate has subsequently gone down.