It is my personal belief that Jim Bowie and his brother Rezin were knifeknuts.
They had many knives and after Jim became famous at the sandbar, he had even more knives

So the most accurate replica is hard to define. Replica of which one? What year? The time of his death at the Alamo or at the sandbar?
Now for your SASS needs you might look at:
Northwoods knives makes a (generic?) bowie that is sambar stag and 1095 steel.
While not huge, it is a real knife.
Check out Vintageknives.com for a pic.
(never did business with them or saw the knife in person)
Bark River Rogue?
Bigger, A2 tool steel and again, a real knife.
Based on the Black design (guardless coffin handle)
Here's the BRKT rouge
(I made the sheath

)
The knife at the Sandbar duel was decribed as 'that big butcher knife' so...you've got alot of leeway there

Here is a big butcher type bowie
This is a repro Marbles Trailmaker. The real Trailmaker is about identical, aluminum pommel instead of stag.
That'll run you a little less than 2Cnotes.
Again, a real knife.
Hope you find this helpful
Here's my favorite (custom) and a book for you to get.
