QRC 3288, if you are in HK you can pick up the two 3.5mm mono jacks to a 3.5mm stereo socket adaptor at almost any plugs and accessories shop. There's 2 competing ones in Admiralty Centre near the bus station end; there's a shop at the end of Thomson Road in Wanchai near Fook Lam Moon and any electronics mall has several - try the one in Southorn Centre, upstairs perhaps. HK Bush in Central?
I hate Radio Shack and the US electronics retailers and hardware stores for this type of thing. Everything is 20 times dearer than here in HK.
My adaptor [used with PXC 250s, actually] does foul the side housing a bit but a smart blow to the plug seems to do the trick every time and no cable crimp or failure so far.