I have been wearing Jockeys for Her for years. There is a small amount of elastic - covered by fabric - and the rest of the entire thing is cotton. Not organic, but cotton and rubber are both bio. The Jockeys are more pricey than the crap cheapo underwear some women by at about $21 for a three pack. They are durable and comfortable, totally worth the money.
I also agree with going commando and doing your kegels!
I just have not found organic undies that inexpensively - and a lot of the organic ones I have tried have not been comfortable. Jockeys bikinis are the best.