Once blood is drawn it's really a risk putting the attacker with another chin, since now you know they can and will attack, and drawing blood shows intent to kill. If only one attacked the other I would say you can try putting the victim with another, but keep in mind not all chins get along, each chin has their own personality. So if you do get another one there is no guarantee it will work out and you may end up with all singles. If both chins attacked, I wouldn't risk another chin with either. Chins can live perfectly happy lives alone, so long as you give them attention everyday, especially if they are still in the same room and can chat to another chin. So really only get another chin if you personally want, have room for, and can handle having possibly another single chin.
I would advise against getting a male just to neuter him, it's a very risky surgery, the chin could die during surgery or after during recovery. It's also a very painful and invasive surgery, so you may need to be home to feed him and give painkillers round the clock, possibly for weeks (if all goes well recovery is about 2 weeks). It's not the same as getting a cat or dog neutered, there are no known health benefits and it comes with a much higher risk of death and infection. Do a search on the forum here about neutering, you should get the idea. Even if the male survives surgery and recovery you still need to wait a couple months after surgery before you can start intros for all the sperm to be gone, and as I said not all chins get along with all other chins. So you may end up putting the male through risky, unnecessary surgery for him to end up alone anyway. Getting females spayed is even more risky so I wouldn't advise that route either.
One that is already neutered and recovered would work as a possible companion, as would another female, it really doesn't matter, it has more to do with personality then with gender. You just need to make sure they are introduced slowly (it can take months) and before putting them together in one cage fully clean and rearrange the cage so it looks and smells neutral. Also you should quarantine the new chins in a separate room for 30 days regardless before even starting intros. That gives the new one time to settle in, for you to get to know it, and for any illness to show before exposing your current chins.