Sorry, but what's not clear in your post is are you looking for a phone case that does not have the same characteristics of an Apple Silicon case so that it would be easier to place in and remove from a pants pocket OR are you just looking for a third-party silicon case.
Regardless, cases that rely on silicone or rubber will have a higher friction coefficient making them more susceptible to this issue. Whereas, plastic or leather cases may not.
However, three cases that come to mind, would be:
- RhinoShield SolidSuit
- OTOFLY Silicone Case
- SUPCASE UB Grip MagSafe Case