In the past six years I bought two auto-titrating CPAP machines that were advertised on EBAY.  And I bought several Breeze nasal pillow masks.  It is too bad that they aren't sold here anymore.  Last year, when I wanted a small machine to take camping, I bought my last CPAP machine (a Goodknight 420G) from www.cpap-auctions.com/ It fits nicely in my pack.  I bought a small 12V, 7AH amp battery here on EBAY.  It will run the machine for one night, and then needs to be recharged. I recharge it from my car using a Vector battery charger and a 12V power inverter, both of which I bought here on EBAY. 

As long as you know what you are doing and know what pressure level you need your machine set for, you should be able to purchase replacement machines for much cheaper than your medical supply company wants to sell them for.  I had a large power fluctuation that burned out my CPAP when I lived in Ghana, and that was when I bought my first machine from EBAY.  I had to go two weeks without a machine before my Remstar came through the diplomatic pouch.  EBAY was a lifesaver back then.