Greetings!

I know the type you are thinking of. You are not alone in being selective about your DVD cases. There are a bunch of good sites detailing this - 1:2. Here is a good scan of the model you are looking for... From the site, it gives the name / manufacturer as "Amaray". A quick google search turned up a number of different sellers. Here's a good one with a FAQ, good photos and plenty of case options.

I usually get cases and media from one of these three companies below. All sell DVD cases, some with "advanced, push button release", but not with images clear enough to see if it is the kind you like.

CDR Outlet
CD Recordable.com
Univenture