(knife) handle joining mechanism

Dear all,

I am making a new teak handle for my knife, a Gerber Big Rock Camp Knife, but i'm stuck at the joining mechanism. It's a full tang knife, and looks like this newly bought:

the knife without the original handle looks like this:

this is the handle i made myself:



now, my problem: i need a joining mechanism ( the nuts and bolts i use now are a temporary solution, obviously), that fastens the two sides of the handle to the knife. The original handle used an inbus bolt on one side, and a nut that in fact consisted of a hollow inbus bolt:


The problem is, the original bolts & nuts are of low quality and not long enough, and i don't know where to find these parts, neither do i know their name. The original 'nut' (or hollow bolt) has a diameter of 6 mm (0,235 inches), the bolt has a diameter of 4 mm (0,16 inches) . Does anyone have an idea how i can solve this problem in an alternative way? I know I could glue the handle parts to the knife, but i'd rather have it to be removable.

Thanks alot!

J.