If the 85C is made like a pre B CZ85 the spring on/in the right side of the frame holds both the slide release and the right side 85 style slide release.
The left side slide release shaft has a notch in it where the flat meets the round part of the shaft, inside the frame. The right side slide release lever has a notch cut through the hollow shaft (that fits over the left side shaft) at a spot that makes both line up when fully inserted, so the spring leg fits into the slot and down into the notch.
The frame is "double walled" on the right side. Only the outside section has a hole of the correctly diameter for the right side lever. The inside frame section/wall has a hole the right size for the left side release lever shaft.
It should work without the right side lever, but will leave a space/ring around the shaft for some dirt/crud to possibly enter the frame.
Take the slide off, look at the frame. insert the left side slide release/shaft back into the frame and try to wiggle it around. You'll see the inside frame wall/section support the shaft.
If your CZ85C is missing the right side lever you can buy one from CZ USA. Or, if you don't want it for some reason, making that bushing to fill in the hole might not be tough, but remember that slot required by the spring so it can hold the left side slide release in place.
This is my CZ75 Compact I drilled the frame on and installed CZ85 slide release levers.
Easy to see the outside (thin frame wall/rail), inside (thicker frame section that supports the left side slide release shaft), you can see the spring leg between the two frame sections and both levers.
I've converted two CZ75s to use CZ85 slide release levers. Only the outside section of the frame needs to be opened up since the right side lever doesn't protrude very far into the frame.
