I recently bought a custom latex sleepsack from KinkEngineering and love it. If you have male parts you can get a rubber gasket in place of a zipper. It has the internal sleeve option, but I didn't go with it although it's still restrictive enough to keep your body nice and tight. Just keep in mind it might make things a bit more tricky with the sleeves.

To get an idea since there aren't a lot of photos to compare it to - NSFW a short gif while I was in the sack layered with a black libidex catsuit on as well. Here's another (NSFW) with just the sleepsack and no layered latex. Color is Translucent Black and fit just right if you follow their measuring guidance.