TM Steyr AUG Civilian - loose outer barrel

[cyberi4n]

Gents - a friend of mine has purchased a second hand TM AUG. It's actually one of my old guns which I sold about 5 years ago, and has had very light skirmish use since then. The forward outer barrel is loose, as the silver "fake gas" retainer that sits under the barrel is missing. I'm assuming that this part is really hard to find? Any suggestions? We can locktite the outer barrel in place as we're unlikely to want to remove it, but it would be good if the original part was available in someone's spares box