Here's the Trila Dress by CROW Clothing. It's made out of soy.

Soy fabric is made from the by-products of tofu manufacturing. This process doesn't require any additional farming. Soy fabric uses minimal manufacturing chemicals in its production, and is biodegradable/compostable.

It has a draw string adjustable waist with a 'Pisces back' opening. You can buy it for $125 or even just $75 depending on your income.