I've developed foot drop in my left foot as a result of a recurring herniated L3/4 disc. 
  
The only place this has impacted my climbing is descending snow while facing out. As I can hardly hold the front of my foot up (i.e., can't stand on left heel), plunge stepping or descending existing steps makes my foot prone to simply rolling forward over the step. And you can guess what happens next. 
  
I sought the advice of PT folks to see if there was an orthotic that I could carry and "throw on" as terrain dictates. A "foot-up brace" was suggested to me - an outside-the-boot device that kinda ties your shoelaces to your calf. 
  
Like so: 
  
 
  
Seems like it's worth a shot. However, if any of y'all have been down this road, I'd like to hear about it.