Large sleeping bag

but the MH Phantom 32 has plenty of room, and the long weighs in at 1 lbs 11 oz, it packs down to the size of a fat nalgene bottle, and I just happen to have one for sale used in the gear swap forum. It is however a mummy bag. The specs are here:
http://www.mountainhardwear.com/Product.aspx?top=1624&cat=1680&prod=2982

Bags are usually measure in shoulder girth. I'm not sure what a 39" width would equate to…..80" girth? I don't know of anything that large off the top of my head.

Check out MEC. They have some 30 or lower rated rectangular down bags, including some wide models. Just be aware that they use celcius (like the rest of the world) so you're looking for about a -3 degree celcius bag.

It's hard to find bags with your desired width since most give the girth and not the width of the bag. I did find two that are close to what are you looking for:

Here's a Sawtooth wide at 35", down and weight isn't too bad.
http://www.campmor.com/outdoor/gear/Product___46440

Trestles wide, synthetic so heavier
http://www.campmor.com/outdoor/gear/Product___46446

Feathered Friends in Seattle has several semi-rectangular and rectangular bags that should meet your criteria.

Feathered friends has good bags, but there store is not up so I have no Idea what the price of anything is or any specs.

This bag from REI looks interesting. It is VERY large but packs to a reasonable size 11"dia by 21" long. I am still trying to figure out what the piece in the middle is.

Here it is:
http://www.rei.com/product/778962