Which is a "real" Bowie knife? The answer is, it depends.
There's the knife Jim Bowie used at the Sandbar Fight. That has been described as a large butcher knife that his brother Rezin claimed to have made and given to Jim for hunting. Whether Rezin actually forged the blade or blacksmiths Clift or Snowden or Black or ... made it from Rezin's "design" is not established as fact.
There are the knives that were given by Rezin and Jim as "tokens" after Jim Bowie's fame spread. These were made by various cutlers and appear to have evolved in shape and complexity and have various levels of ornateness. Some of the knives that stake a claim may or may not have even come from either of the Bowie brothers. The power of the popular hero status Jim Bowie had motivated any number of people to claim they had a knife that Rezin or Jim gave to them or that the family had inherited.
There are the "commercial" knives that various knifemakers/manufacturers made in the mid 19th C based upon the popular hero status of Jim Bowie.
What does appear to be fact is that Jim Bowie used a pretty simple large "butcher/hunting" knife in the infamous Sandbar Fight in Mississippi. His brother Rezin either made or had it made. Later he used a knife to defend himself against hired killers in TX. That may, or may not, have been Black's knife. After Jim became famous the knife evolved as the brothers had various cutlers make "Bowie knives" to give as tokens to admirers or people they wanted to influence. Whether Jim Bowie carried any one of these evolved patterns for any extended period of time is hotly debated. There's nothing directly from him saying he did or didn't, but there are a whole raft of correspondence from the period indicating he did. There's every reason to think that outside of "polite" society he did. Who the makers of some of these knives that are attributed to the Bowie brothers is also hotly debated by historians and authorities on the knife itself. Searles and Black being the most commonly discussed.
Then there's the 19thC "commercial" Bowie Knives that makers that had no relationship to the Bowie brothers made. These were made in America and Sheffield and played off the notoriety of Jim Bowie and the mythology around him and "Bowie's knife" to fill the demand.
So, depending upon perspective ALL six of those knives are "Bowie Knives" (and that's leaving out all the secondary bowies from "back east" American knife makers and those from Sheffield), but
not one of them can be
proven to be "the" knife Jim Bowie used at the Sandbar or the Alamo.
See how difficult it gets to be when an iconic item is lost in history and it's characteristics have to be pieced together from old correspondence, oral history, vague newspaper articles, hotly debated opinions of historians and knife experts, and
then fight with what "everyone knows".