You cannot find the fabric used for judogi for sale in the US unless you are willing to buy a bolt, in which case you can find somebody to act as a middleman between you and the mills in Pakistan where it is all woven. The minimum order last time I checked was 50 meters. If you decide you want to go that route, I can probably put you in touch with a jujitsu school/gi maker who would be an honest intermediary.
What I have found useful substitutions are natural undyed hemp or organic cotton, in either twill or herringbone weaves. There are a number of companies selling them online retail by the yard.
I have bought hemp from http://www.hempbasics.com/
and both hemp and cotton from http://www.nearseanaturals.com/
I have NEVER seen a good gi fabric in a local fabric store, even here in the SF area.