Ultralight Bivy

I need a good water proof Bivy that is as light as possible. Web searches havn't helped me much so im asking here. Ill will be useing the bivy snow, rain, and shine. The bivy needs to be as light as possible with a durable bottom. I have a budget of around $100. Please place your suggestions and links to the site where I can buy it. I also your request that your suggestions are not a poncho bivy mix or a bug net.
-Nate-

Here is something to consider.
Miles gear

I haven't used them yet, but have been thinking about it.

I used an Integral Designs bivy for six months on the AT and had very few problems. ID is a Canadian company and I got mine from MEC. But I don't think I would do that again without a tarp. I still use a tarp/poncho for shelter, but I carry rain gear as well. Even though my experience was good, I would not recommend the bivy alone. Besides, you need some rain protection anyway, so use a poncho and you have your tarp. best, jcp

There is the SOL Escape Bivy.

You could make your own UL bivy pretty easy using a variety of off the shelf or reclaimed materials. I made a UL tent using SOL Emergency Blankets, clear Duct Tape, and a bit of sewing. I'd think it'd be pretty easy to make a bivy too.

The Eureka Solataire is light, and you can get those for under $100. I had one, but found I'm not really a big fan of bivys after using it.

There are weatherproof bivies that weigh as much, and sometimes cost more, than a tent. Then there are ultralight bivies that are actually sleeping bag covers for use with a light tarp. Never seen one (except maybe used) that cost less than $100 with maybe the exception of the silnylon/ripstop versions that are less breathable.

You are not going to get a weatherproof bivy that is ultralight.

what ID bivy did you use.
-Nate-

It says Breathable - but it isn't. I have one... nothing like waking up clammy.