Yes, we do have the o-rings.
The o-rings are all located on this page with all the parts you need for your system:
http://www.waterfilters.net/GE-FX12P-Carbon-Pre-and-Post-RO-Filter_p_0-360.html
I think you are looking for the WS03X10001 o-rings specifically:
http://www.waterfilters.net/GE-WS03X10001-ORing_p_0-592.html
The WS03X10028 o-ring is used with the housing sump:
http://www.waterfilters.net/GE-WS03X10028-Reverse-Osmosis-Filter-ORing_p_0-594.html
Thank you,
WaterFilters.NET