KA-BARs are decent, but they're big and less flexible for carry. If you're not gonna carry it on a study belt, then you need to get some kind of custom clip/mount and sheath, which adds to the 70-200 dollar price tag of their knives. Boot knives are better.
I recommend you go with the Smith and Wesson HRT9B (in your picture), if you want a cheap and adaptable knife. It's a medium sized boot knife that can be used for general purpose defense. Basically a 9 inch overall length, 5 inch bladed, rebranded M-TECH dagger, with a good sheath. Double-edged dagger blade (Don't get the HRT9BF, it has a fake double edge for cucked states/countries) made of Chinese 8Cr13MoV steel that takes a good edge you'll realistically only need to use once. It has a stiff rubber-like wasp-waist handle with a wide double handguard and lanyard hole. Very comfortable and secure in the average hand.
The leather sheath is what you're paying the extra 10 dollars for over an M-TECH variant. Decent with a snap-button thumb break retention system that will no doubt keep your knife from slipping/shaking out even when upside down or being active. It also has a sturdy belt-clip riveted into it, allowing you to clip it to any type of pants/boot/jacket/etc to carry, since the thumb break retention system allows you to retrieve your knife with almost zero effort/noise once you open it up, unlike a kydex sheath that requires you to overcome a few pounds of force and make an audible "CLOCK" to do so. Drawing is much more discreet, especially when you unbutton it concealed with clothes over it.
As a ~20 dollar knife, for self-defense, that you don't need to fuck around with Tek-Loks or fancy little mounting gadgets to carry it well, fits good in your hand for when you really need it, that won't be much of a big deal if you need to dispose of it, it's the quintessential fixed blade in that category and price range.
Be sure to sharpen it, because it comes with a shit factory edge, like most chineseium cutlery. Be careful when you're carrying it, as it can print and be uncomfortable if you don't orient it right or wear tight clothes. Be aware of your local laws, because carrying a fixed or double edged blade may be illegal.