There are the sort of cradles that are used in shops, however I don't know where you'd get one - I'm guessing you'll need to MacGyver something together yourself - just don't secure anything to that infamously femmer Samsung rear panel

 

------>You may want to check Amazon. There are number of such products.
Look into related cattegory and other products for more variety.

 

Since the back of the S4 is removable, I cannot see that this would work very well. On an iPhone (or sadly the S5 if the rumours are true) but not the S4.

 

Could use one of those aluminium frames, and super glue the anti theft to the back cover. The covers are not costly, I wouldn't mind wasting one away. While the aluminium frame, hold it from coming off.
This is the bumper case I have in mind, seem like it would secure the back cover from coming off:

Aluminum Bumper Frame Case for Galaxy S4 i9500 Silver - Galaxys4flipcase.com

 

I hear you, people in this world have sticky fingers and will steal anything and everything. I came up with a few ideas, not sure if they will work.. Just trying to help you brain storm...

Idea #1: A small little 'store display like' stand that I found on amazon, not sure how secure it will be, however i'm sure you can modify it just a little to make it work. Take a look at the links below:

[Aftermarket Product] Brand New Black Anti-Theft Security Telescopic Cell Mobile Phone Display Stand Holder Unit

[Aftermarket Product] Brand New Anti-Theft Security Alarm Charging Display Stand Holder For Mobile Phone Digital Camera

Idea #2: Drill a hole through the side of a case, put some sort of screw-loop with a flush screw head on the inside so the phone still fits inside of the case. Then when there is a loop on the outside of your case you can run a cable like the link I have below through the loop and maybe secure it to your cab. Maybe be a little 'hokey' but i'm sure it would work.

Buggyguard Anti-Theft Retractable Stroller Lock

Idea #3: A secure bag, I'm not sure if this would work because i'm assuming you need to see the screen, but it's a suggestion. A secure bag that is secured to your cab.

Travelon Anti-Theft Lock-Down Pouch