In Jakarta, you can get some Indonesian traditional weapons in Pasaraya Blok M. In Grand Indonesia's Alun-Alun, you also can get several kerises. If you like to go to traditional market, you can go to Pasar Rawa Bening or Pasar Jatinegara. You will find some kerises, badiks, rencongs, goloks, and some replicas of Dutch saber. If you are lucky, you might get a tongkat made from galih kelor, which considered rare.
In Lapangan Tembak Senayan, you can find Husky's products which made kujangs, belatis, kukris, etc.
All these places are well-known to taxi drivers.