We are planning a trip to Switzerland and many of the high peaks are 10,000 feet high or more. Does anyone have any advice on how/where to purchase or rent a small oxygen system as my wife has issues with very high altitudes. Thanks!
Check with a medical supply store in your area. Check with your doctor also. Your wife might need a prescription.
In addition to what Chris wrote... how high do you plan to ascend? Places like Mürren and Zermatt sit at about 1500 m (5000 ft or so). The oxygen tension at this elevation shouldn't cause any problems for anyone except those with the most severe respiratory problems, and such people would probably be too sick to travel anyway. I don't know your wife's medical issues, but unless she normally requires oxygen in her daily life, I could only imagine a problem if you try to ascend on one of the high mountain excursions.
The summits of the Jungfrau, Matterhorn and Monte Rosa are all above 4000m, but unless she's a mountaineer, she won't ascend that high.
Cabin altitude on the way over will be between six and eight thousand.
During climb, it'll probably be set at ten but may or may not get that high for a little while.