There are two ways to do it. Both are a pain in the a$$. If you have at the patience and the time you can call up Fabrikat and have them send you over one of their custom exposed turrets. They are located in Austria, and from experience customs can be quite a hold up on these packages.
The second way is find someone oversees that lives where Kahles has sold the flip top turret and pay them so send you one. I am not sure if these are even available any more or how many of these were ever made, but they are very hard to come by.
I tried both. The Fabrikat piece is very high quality, but no zero stop and no way to prevent it from moving. It moved on me during my first competition. I drew an arrow on top, similar to the LRHS with a paint pen so I would no if it happened again...it still bugged me.
The flip top turret is great as it is protected from moving and has zero stop. I also like that you can't really get lost in the flip top version as it stops just shy of 1 full turret rotation. Its all you need on a LPVO and keeps things very simple.
Here is pics of both options: