I am in the market for a collapsible M4S90 stock as well and am thus in direct competition with you for that resource.
However, I am more than happy to help you with the tubes.
www.carriercomp.com is Kip's website and will provide different contact methods for you to use. Kip is very busy, be forewarned.
This is a thread/page in which you can find SOCOMguy's information:
http://www.benelliusa.com/forum/showthread.php?t=16367&page=12
They are not OEM, both are superior to OEM.