In his article he said "Well, you can go out and buy a real Balisong knife but, if you don’t know what you are doing, you can easily cut yourself. Not a fun experience, trust me. " This is a very true statement since cutting yourself sucks.
Konstantine mentions how to make a Balisong trainer at home with a cheap $8 flea market balisong knife. You do it by wrapping the blade with electrical tape. You can also use loctite to prevent the screws from falling out. However, he highly recommends real balisong trainers because they have higher quality than flea market balisongs but for the same price.
One thing Konstantine heavily noted in the article that a lot of balisong trainers are only made to last a few weeks: long enough for the user to learn how to flip and move on to a real knife. Don't expect your trainer to last forever he says: it is a trainer after all. You can read more here http://bestmachete.net/