Where can I find an outer barrel extender?

[Edrof]

Evening chaps,

I have a G&G GR15 Raider CQB and I would like to lengthen the barrel for cosmetic reasons (plus my Gemtech Halo Silencer doesn't quite seat properly on the CQB-ness). Now, I'd rather not have to swap out the whole barrel (I'm assuming this is a bit hard for numpties) so was rather hoping a simple screw-on affair existed. Google sort of says yes, but nothing conclusive in this country. Has anyone found one? Or should I start learning how to tinker with the barrel?

I need this bit:

to go on this:


Any assistance much appreciated!