Sounds like you have a later production CS45. The earlier ones came with the single side manual safety/decocker.
That being the case, the ambi assembly in the CS45 can be replaced with a single-sided assembly.
It does, however, require some knowledge of stripping the slide and installing the other assembly.
It also requires checking the decocking timing afterward to see if a new sear release lever has to be fitted to work with the new safety/decocker assembly. Since fitting the sear release lever requires filing, and knowing how to identify when the decocking timing is within the recommended range, it's not a kitchen table project for someone unfamiliar with working on S&W pistols.
It's possible for the new assembly to be installed and have its relationship with the existing sear release lever result in working tolerances which fall within the recommended range and provide for proper decocking, but it doesn't happen nearly as often as most armorers would wish.
Bad things can happen when people tinker with firearms without knowing what they're doing and how to properly do it.
For example, if you were to mix up the ambi lever plunger spring and the safety body plunger spring and put the ambi spring under the safety body plunger ... the pistol might decock itself each time it's fired. Not good.
Probably best left to someone who has some knowledge and experience in making the switch.
BTW, the ambi assembly costs more than the single-sided assembly. That little ambi lever is surprisingly pretty expensive all on its own.