I think this is a Straits Bugis keris. A regular Riau-style jawa demam would be perfect.
The sheath would probably liven up after some oiling and buffing with wax.
The buntut can just be a flat simple oval piece that is slightly larger than the batang. If the inward taper due to wear and tear at the end of the batang bothers you, maybe you can have a silver buntut made with an extension to cover that part.