Hi Blue Lander,
Yes you are absolutely right. You are supposed, as a collector, to re-establish the piece as close as it was when it was created. So, probably Javanese - my "nose" says but I can't be sure, around 50-100 years old; please someone more experienced than me is allowed to deny what I just "feel". I would choose a nice vintage wood, simply carved but with a good smooth patina hilt. It will match perfectly I guess, especially if you can find a wood of same color as the sheath.