It can be created by taking an uncharged crystal weapon seed to Eluned in the Ithell Clan district and paying a fee (which seemingly varies similarly to Ilfeen's recharge price scale) of 200,000 to 1,000,000 coins. Alternately, if you have 75 Smithing, you can make the off-hand chakram yourself with Crystal Singing, at the crystal bowl in the Ithell Clan district of Prifddinas. This requires a crystal weapon seed and 375 harmonic dust, and gives 375 Smithing experience.