Whilst I'm sure doing Yoga is advantageous to climbing, I was hoping for suggestions of exercises that are a little more focused.
Sorry if the one word answer seemed facile. It wasn't. I'm not sure yoga is directly advantageous to climbing, what it is extremely useful for is ironing out muscle imbalances. The whole point is to create a flexible, balanced physique. You do a lot of exercises where your wrists are load bearing whilst moving, plus a few where the wrists are flexed under muscle tension/ compression. I had a fair bit of wrist pain/ instability when I started, never bothered me since.
A targeted curl with a dumbell work, but in my experience its a bit like that game where you try to twat a gopher with a golf club. Soon enough it'll pop up elsewhere.