I recently purchased an oversized down comforter from overstock.com that was that size and love it. See the link below. It was the largest one I could find, and I wish I'd even found one a bit bigger for our king bed but it's so much better than the size they usually are and covers the mattress quite well. This one also happens to be a very high fill, so very warm. We like that because DH loves to be warm, I love soft fluffy covers, and we sleep with a window open. Overstock might have others now as well. What's nice is that at least they show the measurements.

For the duvet cover I found an oversized one at csn.com (now it's called wayfair.com) that was about the same size--slightly smaller unfortunately 110 x 96 but works ok, and the price was great. Again I would still love to find even a slightly bigger duvet cover someday because my mattress is so tall. The one I got is Chelsea Frank brand called Emma--white tone on tone stripe with cording. They had great service and shipping was free as well as return shipping if needed. I agree that size is hard to find. Here's the link for that one, and there are others in that brand that are the same size, but I'm not sure if they're the same weight. I particularly like the weight of mine, but did have to iron it after washing it, but daily use seems to not wrinkle it much. Chelsea Frank Duvet cover HTH.

Here is a link that might be useful: Overstock.com 108 x 98 down comforter

I just bought a king for my queen bed down comforter. If I put it on the way it is "supposed" to go - its way to large for my queen bed. But, I put it sideways instead - it's perfect, just enough to tuck under the matress and enough at the top for me too.

I got mine on super sale at Macy's - it was $150.00 for $27.00!!! What a bargin -it's soooo soft! It is cotton with a tough of polyester - it feels like all cotton, but it didn't wrinkle when washed. I believe it was 350 thread count. I love it !!

bixa - I've purchased quite a few down comforters from The Company Store and I either buy their comforter covers or sew my own duvets which is really easy.

Their regular King is 110x98 and they have a lot to pick from. They also sell oversize duvets that are 118 x 98.

Would a 110 x 98 comforter fit properly in a 118 x 98 duvet?