Besides the Otterbox Defender, are there any other cases with integrated screen protector?
There is also the Ballistic HC. This case is similar in concept to the Seidio (smaller inner layer that can be used by itself, or surrounded with the additional outer rubber layer), and also has a built in screen protector. The inner hard case (which has the built in protector) when used without the additional outer rubber layer isn't quite as thick as the Otterbox Defender, so this might satisfy your "thickness" requirements.
http://www.goballisticcase.com/products/iphone-4-ballistic-hc-series-case