$1911

If it's even possible, how do I make a buckle for a bracelet that has an odd amount of strings?

That's explained in the tutorial for the larkshead knot buckle
The string will be inside the loop, but only one end will be used for knotting the pattern. The other end can be cut of close under the loop.

I often make multi-colored buckles by switching to a different string after a few lark's head knots. If you use the odd string somewhere in the middle it will be anchored and will not slip out.

Thank you, both of you were much help ❤️ !