Wow, tough paper, but interesting. It's always a struggle finding sources of info, especially ones that you can reference and are authoritative. If your question is only which two cultures to choose, that's easy. In an academic setting ALWAYS follow what your advisor says, both in terms of his suggestions and his political opinions/leanings (if that's an issue). Your interest is to pass the paper.
If your advisor is pushing you to go down the Java/Kris path, then I can only strongly advise you to take it. It's not a bad idea, especially considering you've, smartly, chosen Japan as the other culture. I see a big similarity between the two. BOTH the Japanese Samurai with their Katana and the Javanese warriors with their Kris blades used to apply a near religious/spiritual devotion and power to their blades. They also used to pass down the blades through the generations where they became more than just effective weapons; they became family treasures. The closest that I've seen so far can be seen by the Maori (indigenous people of New Zealand) with a particular weapon called a Mere (specifically when it was made out of puonamu--aka Jade), but that's not a blade type weapon.
I hope you find the sources you're after. Sorry, this isn't my area of expertise.
Best of luck!