As a lefty myself, I have to say I only buy ambidextrous user knives, with a couple of exceptions, those being LH large and small sebbies which I haven't carried or used in quite awhile. In fact, I know I own them, but I'm uncertain of there whereabouts. The reason, I only buy ambi users is quite simple, if I want to sell it, I can. Without difficulty. Our left handed club, unfortunately knocks out 90% of the resale market, so if you ever plan on selling the knife, you're caught with the very short end of the stick. Most of the time, I'm not worried about closing the knife easily, as I am about opening it. Certainly, doing it the way the rest of the population does, is alot easier, but as you well know, lefties, have learned to adapt. The only thing I care about on a handgun is ambi safeties, the rest, I can work with.
Now, why do I have lefty large and small sebbies? Because I was able to get them....cheap! Why was I able to get them cheap? There is a low demand for left handed only knives.
Since I own enough "user knives" to equip 3 companies of troops with folders, and can't recall where I placed my two sebbies, my advice would be to re-evaluate YOUR knife needs, and look at what is available in the market. Sure if you can "steal" a large LH sebbie, that's been "previously loved" by alll means do so. The Benchmade axis locks are excellent "everybody friendly" and won't kill the bank account, same can be said for a number of Kershaw and SOG knives as well.
That being said, if you're set on a CRK, I would probably go with a standard Umnuzaan, because it will hold most of it's value and it's easy to sell.
Back to the knife, if it will be "much carried and little used" why a bigger knife? If it's for personal defense, I can see that, fortunately here in the U.S., we're still allowed the "1 finger karate", at least for now....