I am going to be a debbie-downer and suggest you buy the cheapest knife that will accomplish your task and that you can afford to lose-and then spend money on training. I've owned, and lost, alot of the big names and I've come to the conclusion that a cheap sharp knife will open MREs and kill a dude just as dead as a sharp expensive knife. I suggest you mozy on down to the PX, (or hardware store, if you are away from a base) and buy yourself a pair of CRKT knives. Get 2 folders, or some sort of fixed blade, whatever you want. Don't worry about the laws of what you can carry in Texas, everyone carries a knife and nobody's gonna care unless you are up to no good. If that's the case, a cop will just use the knife as a reason to fuck with you. If you use it, well, deadly force is deadly force, you better be right in applying it, no matter what the weapon.
Next, go to Takknife.com and order two lexan training knives of the same type of knives that you bought. (One is for you, one is for your training partner.) Then seek out a local Filipino Martial Arts School (my fav is Doce Pares, Pikiti Tirsia Kali) and practice your ass off. One handed, two handed, primary hand, support hand. Practice dropping a knife, switching hands, switching grips, make it unconscious movement, just like with your firearm. After training PTK a while, you will be a very efficient user of a knife, and you will start to develop instincts that you can then develop into defenses to knife attack. It's a progression, though. Stick with it and eventually, you will get to a place where you, with the help of your training partner, will experience an epiphany in attack and defense movement called hubud. Try it out and let me know when you feel that unconscious flowing movement. You'll grin ear to ear and have trouble concentrating the moment you do. It sounds like metaphysical horseshit, I know, but those who have experienced this know what I am talking about. Keep it up and you'll get slick and learn counterattack moves called ginunting, which are very effective means of cutting while blocking and setting up for counter attacks.
There's a reason people come from all over the world to take firearms training in the U.S.: we are a gun culture, good or bad, we fight with guns all the time, and we're good at it. Filipinos know knives because they are a knife culture. Period. They still mix it up on the streets and they (PTK) still have kept their edge as a Combat System, a REAL martial art, as opposed to the watered down pussified politically correct bullshit that is taught in the stripmalls of America.
In conclusion, if you go with a widely available knife, like CRKT, you can buy one at ANY PX in the world (as I have had to do cuz fuckers in foreign countries took my knives at the airport!) for 27 dollars each, or if there's no PX, there will be plenty of shops where you can find a cheap Chinese copy of what you had. Just sharpen it. Also, if you can't find a PTK school nearby, the miracle of the internet will allow you to train yourself with lessons posted on Youtube. That's right, my kid learned to play guitar from Youtube and his buddies, not the expensive guitar lessons I bought him. You can learn PTK attack templates, ginunting moves, plenty of shit you can practice and use to pass the time when you are bored overseas. You can spend hours teaching your buddies what you know, and they will love it. Here's a resource:
http://www.texaskali.org/index.html
TTFWIW
I am looking a good quality knife , under $500-600 to wear, so it should max 5.5" long blade in Texas.. I like the way of the looking of the M1 Aviator, on the relentlessknives.com , but i don't know anything about quality. This knife has a 6" long blade, but they can make it to 5.5". Please help me out if you know any other brand, with a same looking, or if you can educate me a bit about this one 
