That specific conbination is indeed rare, but there are 33 prefixes with chaos res and 5 suffixes. That’s the only thing you really need given the other greens have the same affixes. But that surely won’t be the case unless you gdstash the exact build or I send you my file, so what you should do is put into grimtools everything you have minus the amulet and then look at your amulet copies and check whatever caps resists. If there’s nothing then keep farming. What’s in my build aren’t really BiS. There are much rarer combinations that would’ve been better.
Thanks for the reply 
However when i look at your ammy it says it can have like 250% vit dmg, the best one i found so far had like 100% why might this be?
It’s the decay suffix. Gives ~100% to vit. It’s a yellow suffix so it shouldn’t be that rare, but getting the figures in my ammy needs the perfect rolls. It’s just for squeezing every last bit of damage tho. Things like more DA or resists (so you could free up other affixes on the other greens) might be better.
%dmg isn’t really first priority once it’s more than around 2.2k