If you just search for the flights on Expedia or such sites then these fares often come up, but it's sometimes a matter of searching for each individual flight rather than just a round trip or multi-city.
What is better though, is a new tool since the last post:
Book with Matrix where you can just copy/paste results from Matrix (instructions are on the site) and it will try to find it for you.
(In your case though, if it's all Delta flights, they should show up just fine on delta.com. I'm seeing them for $785.81 per person there for those dates unless I'm missing something.)
I've used book with matrix a few times successfully. Lately though I have had a problem where a fare will list on ITA, but book with matrix will send me to travel agents that can't process the fare.