is there an extra large humidifier for resmed s9

[richpress]

I have a Resmed S9 auto CPAP.  I live in Arizona and the humidity is very low.  The heated humidifier does not hold enough water to last all night.  I wake up with a very dry mouth and sometimes that causes canker sores.   

is there an extra large humidifier for resmed s9?   Is there an add-on humidifier that will increase the time I can use the CPAP?  Or, do I need to find a new unit with a much larger water chamber?

[Gideon]

Someone years ago cobbled one together. Basically it was a modified humidifier. A hole was drilled in the top then a water bottle was inserted (actually a tube on the water bottle) was inserted thru the hole into the humidifier chamber. As the water level lowered to below the water level water would flow until it no longer did. there was some issue with holding the bottle up.